i'm just curious, have you tried typing the actual letters on the BB keyboard... it seems if they were smart that would automatically be possible when the phone was in a call
While entering a number to dial or while on the phone (in phone mode), press and hold ALT while typing the usual letter keys. The 8830 sends the corresponding touch-tones. (Cool feature!)
You can also store letters in the same manner in your phone directory -- 1-800-HELPMEE, for example, and the 8830 will dial using the correct tones.