Continuous irritation

Once again I'm being harassed by SB concerning my RCP that you claim to be in the arrears, I have in writing the contract amount that I have been paying back for a number of years. I Increased this amount two year ago and am constantly been called by consultants, sms's and voice messages. I have in writing from a SB employee that I am not in arrears but its a technical issue on your side. I've even been threatened that I will be charged interest on the arrears. I'm slowly getting fed up with your employee's incompetence. Get it right or I'll take this issue further.