I removed a damaged T7208 set from a Norstar system. I replaced it with a T7316 set which was part of a retired 616 system. When I plugged in the T7316 to the working system it retained all of its feature button programming from the 616 system. All the buttons were the same as on the old 616 system. I plugged the phone back into the old system and erased all the buttons. I then plugged the phone back into the new system and it still reverted back to the old settings. I am unable to program the feature buttons while the phone is on the new system because it has set lock enabled. What's the best thing to do? And why is this phone keeping its feature button settings? Does the system match the telephone serial number or something?