Text group problem since upgrade to iOS 6

[Tonipym]

Prior to upgrading my I pad and I phone to ios6 software I used text group constantly without problem.my texts were sent and received from my I phone 4s and synced with my ipad2.since upgrading I can not add new people to my local groups (which have now disappeared) on my i phone but still show and can be added on my ipad, however can only send iMessages. I use this app as a major part of my business and would like some help and advice please, how do I fix this. I have tried to downgrade back to iOS 5 without luck!