Lost access to my Apple ID account

I took my phone into the store on the 9th of Nov. Its been them for more than a month, they don´t communicate at all nor do they reply to emails. I went to the store more than 3 times and I was turned back as they advised that they were still trying to fix it. They issued a report saying that my phone is beyond repairs.. I don't know because when I took it there it was perfectly working besides the LCD issue.

I went to fetch my phone last month (December) the lady at the front desk gave it to me and there was no explanation regarding the progress but since I was in contact with the tech he advised that they managed to switch it on, when I got home tried to charge the device it wasn't responding at all. Today I managed to access my email the one I use as my email ID, I found out that they changed my Apple ID and my password without my permission now I can't even recover it because they changed the phone number as well!! But on the job card they said the phone came in stuck it wasn't responding to anything, if so, how did they change my details and why, now I doubt if this is really my phone.. something is not adding up here! you can't change someone else's Apple ID with a consent. I've been emailing the store, no response at all.