Auto transmission jerks when gear changes

On my 2003 Chevy Impala with 127,000 miles the car jerks like someone has hit you in the rear end, it usually happens from first to second and is becoming more frequent. A recent transmission service had no effect

You’re going to need to take it to your best local, independent (i.e. non-corporate chain) transmission shop. Someone will need to put it on a scanner to check for error codes and watch what the transmission is up to. If you come up with codes and other info you can post them here for comment/advice.

What was done in the recent transmission service? Was the pan dropped and filter changed? Was the transmission ever serviced before this?

Be prepared for bad news.

A recent transmission service had no effect

What was the prior history of transmission service. Was that recent transmission service the first one? I hear a lot of complaints about transmissions that were never serviced until the problems of poorly maintained transmission became apparent. Waiting until you have a problem is too late to prevent it.