When I picked up my bongo early this year the key had a fob which let me lock the doors. The fob is a well worn and held together with tape

Anyhow its stopped working now so I took it to a key cutter and asked for a new battery. He said there was no point buying a new battery as the fob would have to be re programmed by a Mazda dealer. We have a mazda dealer near by but from reading the board they dont seem to keen on bongos.
Is the advice he gave right? I thought a new battery would get it work again.
Will a mazda dealer help me and if so is it expensive?
Many thanks
Travis