Loan Settlement

I have a loan with capitec that was handed over to Vertex for collections and i was called by Consultant and i requested a settlement discount and i was told to write amount that i want to pay and state the reasons and i wanted to settle the loan for R150k but i was informed that Capitec requested that i increase the amount to R174k and i gladly did and revised the amount and paid the the R174k as agreed and now Vertex comes back saying Capitec rejected. the revised settlement of R174k and i must pay more or be refunded. i will not accept the refund and i want this loan settled and i will not incur any additional expenses from this loan. Vertex is playing mind games with me and i will not accept this illtreatment and they must make sure that this loan is paid in full and i will raise dispute with credit bureaur as well