S4 screen repair

My S4 was booked in at Samsung for a screen repair. I waited for more than a month for it to be returned to me. When I received I noticed it went for a QA Test. The side was not straight at all. I took the phone back on a Saturday and they told me they can not assist me I need to return in the week. The screen broke again and my wife returned it for me now it is going again for 3 weeks they want to charge me for the repair. I still have 2 screen repairs left on the phone. I am sending them mails to find out what is going on but with no response from them.