My iphone XR

I bought my iphone in July 2019. in May 2020, when the phone was only ten months old, I phoned apple to report the problem with it. they suggested a "rest". I did that but didn't change. due to my heart problem and Covid 19 I could only come out and book a visit to apple store in September. they say my phone is outside warranty time and I have to pay £190 to repair it. When I told them that I reported the fault within the warranty period and if it was not due to lockdown I could go to them earlier they are asking for the proof of contact that, unfortunately, I don't have. is there anything I can do about this? I am a pensioner with very low income and paying that money is hard. also there are still ten month of the finance instalments left.

Thank