I have the inverse problem -- I receive duplicate texts. Most I've seen has been a total of 4 messages, and that seems to be the most common, but I have seen anywhere from 1 to 3 duplicates. Happens fairly often from an alarm service sending me alert notifications. The service has checked with their ISP, and they assure them that they're sending only one message. These alerts are also sent via e-mail, and I receive (correctly) only one copy.
I see a similar problem with regular e-mail, mostly from one sender. He runs his own sendmail server, and has sent me logs showing:
...four "bad acknowledgement" deferrals by relay.verizon.net, that apparently actually did receive and forward the message anyway; followed by the fifth "normal" message acceptance.
Now I have 2 questions:
(1) How do I find someone within Verizon who knows and cares about something like this, and can maybe fix it?
-and-
(2) Are similar logs and diagnostics available for SMS servers, and if so, see (1).
Actually, there's a 3rd question:
(3) Am I being charged for the duplicate texts?