*gerald_g, if it is an original R134a, most probably they used PAG oil, if your technician recharge it with R12, magkaroon ka ng problema sa iyong lubricant (compressor oil) because it will not mix with R12, in due time puwedeng masira ang iyong compressor because the lack of lubricant circulating in the system.

mabuti gawin mo diyan, recover the R12, dehydrate (vacuum) the system and recharge with R134a.