If I send a group message to multiple groups, are phone numbers who are in 2 or more of these groups receive more than one of the same message?

NO. They will only receive 1 message. The ProTexting platform recognizes this redundancy and will not allow sending a message multiple times to the same phone number for the same Group Text Message Campaign.

In addition, when importing contacts, ProTexting DOES NOT create double entries for the same contact (number). You can then add the unique contact to several groups.