Originally Posted by JSanders
Wirelessly posted (8700g: BlackBerry8800/4.2.1 Profile/MIDP-2.0 Configuration/CLDC-1.1 VendorID/102)
It's been covered, but glad to answer. In replying to an email there is never an option to change the "send using". You cannot change that in replies.
If you must change the send using message service when replying, you need to choose forward and enter the recipient and change the "send using" at the top.
You can also change the send using in original emails you are composing.
There is a solution and it is software based. I think it is BBreply