contract cancellation

i have a contract with Vodacom which i took on 5 may 2020 i defaulted on my account last year for 3 months then paid the amount in full they added another 3 months to my contract which which they explained to me, so my contract which should end 5 may 2022 they say ends on December 2022 7 months added to my contract very unfair and selfish when i call their collections department am asked about getting a copy of my contract pooor service cheating me of the little that i have very disappointed in Vodacom