ACCOUNT I CAN'T GET PAID

Good day! I've been a loyal customer to Mrp for many years. I will be closing my account and no longer supporting them. I was in hospital and unable to pay my account for 3 weeks and when I went online their system wouldn't allocate the payment! Now im getting snotty sms's and there's no way I can contact them to explain even though I've left messages for them to call me back. I have EFT the amount due and want to make sure they allocate it as I will not have a bad payment record because they can't help customers correctly! Extremely disappointed and this isn't the first time I've had issues with my account!