Someone else reported this happening and worked directly with Verizon to fix it... Apparently it was something on Verizon's side. Maybe give them a call & see if they can fix it for you? good luck. (you can probably find the thread using Search).
It's been a problem with Verizon for quite sometime.....it'll happen to me when I text people on other networks and they'll come back to me and say 'you must be on Verizon' as they have the problem on their side also with anyone they text with who has Verizon. They don't have the problem with anyone else on a non-Verizon phone. I haven't had it happen in awhile for me but everyonce in awhile it'll sprout up and annoy me for a day or so
ah some ol **bleep** lol reset your phone yada yada i dunno its just some glitch in verizon because i experience on other phones i know on verizon and non-verizon alike.....oh well annoying but so is being to reset my dang phone for every issue guess what verizon unlock these phones just a bit and you'd save a ton of money by actually being able to trouble shoot the software rather than say reset it and then just replacing it ....lol the lady at my post office thought i was mailing bombs out since i have returned 9 phones in 3 months all in that the little fedex box.
Thank you for bringing this issue to our community and it's members. Although this has been brought to our attention several times, it is difficult to post a universal solution to such an issue. This is because there are so many variables that effect the delivery and duplication of text messages. If you are still experiencing text duplication then you can send me a private message so I can further assist. Please include your full name, the mobile number in question, and a brief summary of the issue. I look forward to assist you with this issue.