what kind of car is it? and what kind of alarm? does your car have a factory alarm or is it key with a chip in it?
how long was the car alarmed till the car doors locked? most alarms have something called passive alarming so when the doors are closed for a set time the car will arm itself and locks the doors.
did he add power locks to your door or just simply add the lock feature to your alarm? it sounds that he should of read his tech notes before tapping into your lock switches.
also what shop did you take it to and what alarms are they authourized to work on. at the shops i've worked at we never installed anything that we didn't sell so we know our product.