1997 Chevy Blazer shifting

Hi, I went to a store the other day and when I shift into park, it did not lock in. When it finally lock into park, I was not able to shift it unless releasing switch in the shifter. Service man at Walmart told me, I will need a transmission cable. I had the car towed to a repair shop. Then they could not find a problem, but I drove the car and when I parked the car, it started to roll back. I uised emergency brake to stop it from rolling. I took it back to shop and they told me that I need a transmission cable because it was stretched. When I picked it up, i went just around a couple blocks, parked and when I cranked the car, I was not able to shift from Park to Reverse, it was locked. I use the release switch in the shifter again to be able to shift it in to reverse and with the shifter placed it into drive. Now, the repair shop has my car and they do not know currently what's wrong until tomorrow. They told me that they were unable to shft at all now. Any suggestion?
Thank you!