UNLOCKED PHONE WONT WORK WITH THAI SIM CARD

Hello! So my friend and I took her phone to Apple to unlock it so I could use it with a different English SIM card. So, I came to Thailand and I’m now living here So need a Thai SIM card. lt was all set up and when he turned the phone on it said that the cellular something wasn’t supported and that it wasn’t a hardware problem but that the phone was locked. So I tried to get online support but it said that my phone isn’t registered For that. Please someone help me, I can’t afford a new phone and I really don’t understand what I have to do next.