IMEI STILL LOCKED AFTER CONTRACT IS DONE

I have Purchased a Samsung galaxy A-12 IMEI -*** dual sim so when I took the contract it said that the first sim slot is network locked for the first 12 months I was then explained by the sales person how it works I purchased the phone in March 2022 its now June 2023 I've been to 3 stores already the 2 mtn stores in eastgate shopping center and in Bedford view. All 3 stores says to me that the phone is permanently network locked and that there's no way to unlock it I have to keep using an mtn sim card for the phone to work. I contacted customercare they sent me a link which I have to pay over a R1000 for it to be unlocked i was not told this when i purchased the phone. This is ridiculous what type of **** is this company running .they are forcing people to use there network with all there lies and *******