I'd advise calling general support, so they can take a look at the list's formatting and help with getting it imported for you live.
If you're unable to call, please reply directly to the automated @ mention email you receive from this response. In the reply email, please include your account username and attach the contact file. The file will need to at least include the email address of the contact, their SMS number, and the SMS consent date in the yyyy-mm-dd format.
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