nope

andylene said:
If I wanted to add a text messaging plan to my service, would I have to resign a contract? Thanks.

Not at all. Your contract does not confine you to a particular price plan or set of features. Sometimes certain offers require a new contract (the biggest example, for a long time, was a customer going from a plan without mobile to mobile minutes to an M2M voice plan, which would require a new 11 month contract). Even if you did pick such an offer, it does not require you to cancel - the new contract just takes the place of the old one.

That said, most customers only ever encounter contract renewals when purchasing new equipment at a discounted price. It's been ages since I've had to actual...
(continues)

i don't know of a carrier that would.