Lack off communication.

I was contacted by Cell c regarding my account by a social media consultant named Busiswa I sent her my paid up letter and I also requested proof that my account was closed officially it's been more than 7 days now I not received any communication yet they where quick to say that I owe them without them checking their systems now that I want proof they dragging their feet yet wen they requested a paid up letter from me I didn't delay them .