Invading my privacy

I have been a customer for MTN since 01 December 2016. My phone has a problem with a speaker and have submitted it on the 12 February 2021 to be fixed. I have not received it back but what have picked up is that the person who is fixing my phone is busy reading my messages, which clearly tell me instead of fixing my phone he/she is busy going through my personal stuff and I do not think that is allowed. I sent an email to Mtn Complaints about this and no one has responded about it. Its almost 2 weeks now and I haven't not received my phone back.