I rehab CTR surgeries frequently at work and they're perfectly effective. The only possibly way for them to cut the carpal tunnel band and it not reduce the symptoms completely, is if they misdiagnosed it and the root of the problem was further up the arm, like maybe ulnar nerve compression or something else being compressed in the brachial plexus.

Has your doctor or surgeon had you go through a nerve conduction study yet? It's a fool proof way for them to find out where your nerve is compressed.