Tech destroys phone during a battery replacement

Shocker, Phone broken when replacing a battery I went to replace my iphone battery. Thinners was poured onto the battery, to help remove the glue, it should be dipped on cotton wool and then rubbed on the glue. He asked to work on it to try to fix it, i left and returned about an hour later, to find the tech and my phone were no longer at the shop. On his return he handed me my broken phone, offered my an old usediphone 7 or 8, i requested 8 but was given a 7, cannot even run whatsapp.; I was forced to buy a new phone yeterday. I am a pensioner. He owes me for a phone