Hi Team.

So My iphone now seems to regularly failing to send SMS messages. I have good cell signal*

I have tried resetting the phone to factory settings in itunes deleting all data and setting phone up as new and the issue remains you name it I've tried it I've also tried a couple of Sim Cards 

I've called vodafone and they reset something at their end which hasn't helped. it did seem to only be long messages that would fail now it's even short ones and it's very often and if I get a text from someone I will try to reply a couple of times but then have to give up (Error Message sending failed)  it's getting very annoying.

I am running the latest version of IOS 11. Calls don't drop and mobile data work fine. Does this sound like a hardware issue? Should I take it into a apple authorised repair agent? I was going to wait till November/december before I went to one (to get my cheap battery replacement) But if this is a hardware issue I better take it in now cause it's under warranty till September  (Purchased at launch)

Thanks ~