2003 Chevy Trailblazer

While driving oneday the vehicle stopped changing gears. It will go in reverse and it will go in first gear but after that the engine just revs up but will not change to the next gear. Is the transmission gone? Someone told me that its all electronic and that there is computer chip that is suposed to send a message to the transmission to change gears. Someone else told me that the strainer needs to cleaned out. And another couch mechanic told me that there are bands in there that may be broken. I don't know what to think. I just can't afford to purchase a whole new transmission right now. If someone has any sound advice please pass it on.

Thanks,
Stuck in 1st