Unsatisfied with my back payment

With Metropolitan I had hospital plan, because was busy with late my mother's funeral arrangement that was the reason claimed end of July for my cash back. Beginning of August I climbed the office to cancel and was told to send sms which I did and they reply to say I must write a letter and sign it. That was difficult for me because I'm disabled partially blind and still at home no laptop to write and print & sign and the end up deducting my payslip for August & September, now I'm not satisfied with outcome coz I went to the branche on Friday but they only back pay me for only one month don't know why.