USELESSSSSSSSSSSSSS

I am so angry , im strugling for 1 month to change my email address on their system!!! they are always coming with some story, then they ask for a signed letter, when i do that they dont accept it, or they say they cant find me on the system at all... The people are rude as hell! (the one i spoke to) i asked them to change my address, and ive sent proof of address but no they cant. SO IF YOU WANT MY INSTALLMENT ??? WILL YOU HAVE ALL MY DETAILS THEN?????