Mytrip.com complaint: MyTrip completed messed up my Order request

My order is LJRM8C. There are two Lufthansa bookings on my order. One belongs to me (RD5WVX) and the other belongs to my father (LGCP8L). On Monday Dec 5th. I had made a request to MyTrip to change the return date on my Father’s booking LGCP8L from Jan 11th to March 29th. I had specifically given my father’s booking details and paid the $125 for their date change service.
The next day I found out that the MyTrip agent by mistake changed the return date on my Booking RD5WVX instead of my father’s booking LGCP8L. Now, when I am calling them everyday and asking them to correct their mistake, they are delaying and making excuses that they will be doing some kind of a Call listening. My question is, why have they waited for a week to correct a mistake they made. My flight is on the 21st and they need to fix this ASAP. I have recordings of calls made to MyTrip as evidence.