Littlewoods

I have for the past 6 weeks been trying to get littlewoods to send me archive statements for April, May and June 2016. These statements are relevant to a large overpayment i made back then when clearing my entire balance. What i didnt realise at the time was that a large part of the balance had been made up of bnpl projected interest which isnt payable unless one misses the deadline. I would like littlewoods to investigate the overpayment and send me the statements requested. I have been hitting a brick wall up to now. I have written letters, sent webmail , emails and phoned all to no avail. Please help.