paid off my loan but still get emails and debits ! **** of a COMPANY

i had a load with fasta and paid it off with jer associates which is their legal team i belive. i called to get the settelment letter months ago and it was not given to me yet they confirmed that my loan was paid off... fasta has no call center and now they are telling me i owe them that load amount i paid, i sent a query and till date i dont get assistance. i require fasta to call me and sort this thing sice i cant get hold of them. worst load company ever