Q: My iPhone number format (+237 6XXXXXXXX) is not accepted for verification in order to receive a validation code

I'm from Cameroon and the telephone number format was changed. Its format is as follows:

+237 6XXXXXXXX. This format is not accepted when it comes to receive a validation code for confirmation as a device. What should I do so that I can receive your sms? The only format accepted is +237 XXXXXXXX but with this format I cannot receive your sent validation code sms