Fasta payment

Had a loan with Fasta beginning of Dec, on the 3rd of January 2024 I paid the entire balance without them even having to deduct first installment, I woke up this morning to a text of payment reminder, went on the site to check my balance only to find that according to them I still owe them the entire amount, 30 minutes ago they deducted R170 from my account, I hv no idea what that is for because the payment arrangement was R1800. This is very annoying.