You can modify the format of your Phone number field to match your needs. After you have added the field to your form, in the left side panel, under the Validation section, you can find Number format.
By default, the standard format for Phone number field is set on 3-3-4, but you have plenty of options to choose from. The number format of 3-3-4 means that the field will accept only phone numbers that have the format of 3 digits – 3 digits – 4 digits (e.g: 123-456-7891).
If by any chance you can not find your country’s standard format, you can use a Short answer field instead. This will not limit users to a specific format and you can also enable the Prefix option.
You can also set the field validation to regular expression where you can add the regex code to define your desired phone number format.