Late payment markers on file even though I’m not meant to be paying yet

LMS93

Hello

Looking for some help. Basically I handed a car back to the finance company after my 3 year contract ended, I handed this back in September/October 2018. All payments till the point of end of contract were up to date and had been paid. Since Then I’ve not had to pay anything, and was told by the company I wouldn’t have to until they had sold the car at auction and sent me a bill and I can then make a payment plan.

I still haven’t received a bill but have today noticed every month since the contract had ended they have been putting a late payment marker on my credit file!

I’ve disputed this today with them and insisted they remove these as I’ve not missed any payments as the contract had ended and I was to wait for the final bill to arrange payments, they’re saying they won’t remove them as there there is an amount outstanding, which I agree there is but was previously explained to me until a payment plan is in place (and unless I miss any payments) nothing will go on my report.

Does anyone know if they can legally put these markers on my file even though my contract ended and I’m not tied to any contract to pay them back each month as of yet?