diff --git a/pagerduty/resource_pagerduty_user_contact_method.go b/pagerduty/resource_pagerduty_user_contact_method.go
index 36a5a34de..14fec0fc6 100644
--- a/pagerduty/resource_pagerduty_user_contact_method.go
+++ b/pagerduty/resource_pagerduty_user_contact_method.go
@@ -23,19 +23,7 @@ func resourcePagerDutyUserContactMethod() *schema.Resource {
 		Importer: &schema.ResourceImporter{
 			State: resourcePagerDutyUserContactMethodImport,
 		},
-		CustomizeDiff: func(context context.Context, diff *schema.ResourceDiff, i interface{}) error {
-			a := diff.Get("address").(string)
-			t := diff.Get("type").(string)
-			if t == "sms_contact_method" || t == "phone_contact_method" {
-				if strings.HasPrefix(a, "0") {
-					return fmt.Errorf("phone numbers starting with a 0 are not supported was %q", a)
-				}
-				if _, err := strconv.Atoi(a); err != nil {
-					return fmt.Errorf("phone number %q is not valid as it contains non-digit characters: %w", a, err)
-				}
-			}
-			return nil
-		},
+		CustomizeDiff: customizeDiffResourceUserContactMethod,
 		Schema: map[string]*schema.Schema{
 			"user_id": {
 				Type:     schema.TypeString,
@@ -88,6 +76,47 @@ func resourcePagerDutyUserContactMethod() *schema.Resource {
 	}
 }
 
+func customizeDiffResourceUserContactMethod(context context.Context, diff *schema.ResourceDiff, i interface{}) error {
+	a := diff.Get("address").(string)
+	t := diff.Get("type").(string)
+	c := diff.Get("country_code").(int)
+
+	if t == "sms_contact_method" || t == "phone_contact_method" {
+		// Validation logic based on https://support.pagerduty.com/docs/user-profile#phone-number-formatting
+		maxLength := 40
+		if len(a) > maxLength {
+			return fmt.Errorf("phone numbers may not exceed 40 characters")
+		}
+		for _, char := range a {
+			isAllowedChar := char == ',' || char == '*' || char == '#'
+			if _, err := strconv.ParseInt(string(char), 10, 64); err != nil && !isAllowedChar {
+				return fmt.Errorf("phone numbers may only include digits from 0-9 and the symbols: comma (,), asterisk (*), and pound (#)")
+			}
+		}
+
+		isMexicoNumber := c == 52
+		if t == "sms_contact_method" && isMexicoNumber && strings.HasPrefix(a, "1") {
+			return fmt.Errorf("Mexico-based SMS numbers should be free of area code prefixes, so please remove the leading 1 in the number %q", a)
+		}
+
+		isTrunkPrefixNotSupported := map[int]string{
+			33: "0", // France (33-0)
+			40: "0", // Romania (40-0)
+			44: "0", // UK (44-0)
+			45: "0", // Denmark (45-0)
+			49: "0", // Germany (49-0)
+			61: "0", // Australia (61-0)
+			66: "0", // Thailand (66-0)
+			91: "0", // India (91-0)
+			1:  "1", // North America (1-1)
+		}
+		if prefix, ok := isTrunkPrefixNotSupported[c]; ok && strings.HasPrefix(a, prefix) {
+			return fmt.Errorf("Trunk prefixes are not supported for following countries and regions: France, Romania, UK, Denmark, Germany, Australia, Thailand, India and North America, so must be formatted for international use without the leading %s", prefix)
+		}
+	}
+	return nil
+}
+
 func buildUserContactMethodStruct(d *schema.ResourceData) *pagerduty.ContactMethod {
 	contactMethod := &pagerduty.ContactMethod{
 		Type:    d.Get("type").(string),
diff --git a/pagerduty/resource_pagerduty_user_contact_method_test.go b/pagerduty/resource_pagerduty_user_contact_method_test.go
index 3e3574779..9806e3863 100644
--- a/pagerduty/resource_pagerduty_user_contact_method_test.go
+++ b/pagerduty/resource_pagerduty_user_contact_method_test.go
@@ -68,6 +68,40 @@ func TestAccPagerDutyUserContactMethodPhone_Basic(t *testing.T) {
 	})
 }
 
+func TestAccPagerDutyUserContactMethodPhone_FormatValidation(t *testing.T) {
+	username := fmt.Sprintf("tf-%s", acctest.RandString(5))
+	email := fmt.Sprintf("%s@foo.test", username)
+	tooLongNumber := "4153013250415301325041530132504153013250,415301325041530132504,530132504153013250"
+
+	resource.Test(t, resource.TestCase{
+		PreCheck:     func() { testAccPreCheck(t) },
+		Providers:    testAccProviders,
+		CheckDestroy: testAccCheckPagerDutyUserContactMethodDestroy,
+		Steps: []resource.TestStep{
+			{
+				Config:      testAccCheckPagerDutyUserContactMethodPhoneFormatValidationConfig(username, email, "phone_contact_method", "1", tooLongNumber),
+				PlanOnly:    true,
+				ExpectError: regexp.MustCompile("phone numbers may not exceed 40 characters"),
+			},
+			{
+				Config:      testAccCheckPagerDutyUserContactMethodPhoneFormatValidationConfig(username, email, "phone_contact_method", "1", "+4153013250"),
+				PlanOnly:    true,
+				ExpectError: regexp.MustCompile("phone numbers may only include digits from 0-9 and the symbols"),
+			},
+			{
+				Config:      testAccCheckPagerDutyUserContactMethodPhoneFormatValidationConfig(username, email, "phone_contact_method", "44", "01332412251"),
+				PlanOnly:    true,
+				ExpectError: regexp.MustCompile("Trunk prefixes are not supported for following countries and regions: France, Romania, UK, Denmark, Germany, Australia, Thailand, India and North America, so must be formatted for international use without the leading 0"),
+			},
+			{
+				Config:      testAccCheckPagerDutyUserContactMethodPhoneFormatValidationConfig(username, email, "sms_contact_method", "52", "15558889999"),
+				PlanOnly:    true,
+				ExpectError: regexp.MustCompile("Mexico-based SMS numbers should be free of area code prefixes, so please remove the leading 1 in the number"),
+			},
+		},
+	})
+}
+
 func TestAccPagerDutyUserContactMethodPhone_EnforceUpdateIfAlreadyExist(t *testing.T) {
 	username := fmt.Sprintf("tf-%s", acctest.RandString(5))
 	email := fmt.Sprintf("%s@foo.test", username)
@@ -281,6 +315,27 @@ resource "pagerduty_user_contact_method" "foo" {
 `, username, email, phone)
 }
 
+func testAccCheckPagerDutyUserContactMethodPhoneFormatValidationConfig(username, email, method_type, countryCode, phone string) string {
+	return fmt.Sprintf(`
+resource "pagerduty_user" "foo" {
+  name        = "%[1]v"
+  email       = "%[2]v"
+  color       = "red"
+  role        = "user"
+  job_title   = "bar"
+  description = "bar"
+}
+
+resource "pagerduty_user_contact_method" "foo" {
+  user_id      = pagerduty_user.foo.id
+  type         = "%[3]s"
+  country_code = "+%[4]s"
+  address      = "%[5]s"
+  label        = "%[1]v"
+}
+`, username, email, method_type, countryCode, phone)
+}
+
 func testAccCheckPagerDutyUserContactMethodSMSConfig(username, email string) string {
 	return fmt.Sprintf(`
 resource "pagerduty_user" "foo" {