Paid up letter and refund due to me!o

I received an account statement from on air on Friday 16 April.Sebn by Sarisha Singh from billing department. To my amazement i have ×5 credits due to me,unexplained! Its a pity i cannot upload the statement here. I have actually overpayed this account. Thats the reason they cannot provide me with a settlement amount. I tried calling her back,but obviously no response,but i responded to the email,demanding answers . I want my refund as well as my paid up letter!. I have not received any response as to why the debit order was not automatically stopped when they realised i payed the acvount in full.. In January and February i was even charged service fee of the same amount as my debit amount! Meaning this account was paid in full in December 2020 i reckon!!