Before sending or matching, Sprwt strips spaces, parentheses and dashes from a phone number. Numbers that already start with + or 00 are used as-is. A number that starts with a single 0 has that 0 removed and your account's default country code prefixed in its place; any other number simply gets that code added to the front. The code is shown next to the "Add country code" checkbox when you import an SMS contact list by CSV (e.g. "Add country code (+1) to contacts?"), so that's a quick way to check what your account is set to. This is why customers who typed a local-format number still receive texts, and inbound texts are matched to customers by the same normalised-number logic. If customers from other countries store local-format numbers, ask them to include the international prefix so the correct country code is used.