Phone not repaired after 6 weeks.

My son took his phone in for repairs. First of all he was told that his insurance would not cover the screen repair because the sim card was out of the phone for too long. Thank you lockdown! He left the phone there, and for a month we didn't hear anything. We tried several times to reach the shop to find out whether it was fixed, to no avail. No answer, ever. After a month we got an sms that the phone was ready to be picked up. He went to collect it, only to be told it was not fixed since they didn't know that he gave the go-ahead to fix the phone. They promised that it would be fixed within a week. Last week we got a message that the phone has been repaired and was ready for collection. My son went in, and the screen was indeed replaced. He switched it on only to see that it didn't come on. Their excuse was oh sorry, the technician didn't actually test to see whether it was working. It is now another week later, and we haven't heard a word from them. They have had six weeks to repair the phone. They are not answering the phone when we call the number they gave us