Fiat Finance Major Pain

tammy73

Hi all
We got an unsecured car loan with fiat finance back in March, unfortunately in August we missed a payment, we agreed a payment plan to make up the missing payment over 3 months, this intially was done over the phone, then it was confirmed in writing, which we stuck to but every month the day after the money goes out Fiat call to say we're in arrears, they're adding admin charges and demanding additional payments. Obviously we don't pay the additional charges and tell them we have an agreement which seems to settle them but we don't know if they are adding admin fees. This is compounded because we changed banks and unfortunately they won't send a new dd mandate so we've set up a standing order.
We've written to customer services several times they don't respond but we do get letters every month about the arrears and charges they are adding.
Getting pretty sick of it and would really like some advise.
Many thanks