Are you nuts?

I had pricelock the last two years. I signed a debit order (they forced me to sign a debit order) and for two years they didn't debit my account. The last two months they now suddenly attempt debit me for R22,000 for the past two years. this was not our agreement. No one has ever phoned me and they have never cut off my services. Not sure I understand why I signed a debit order if they waited two years and now wants 2 years of payments at once?