Bad service

Good day

I am so sad to write this letter to you, i need your assistance, i was having a contact with Vodacom for 24 months, i took 2 phones on August 2021, so i paid that contract for 24 months even thou we agreed on R500 but it changed to R624, i paid them until 26th of August 2023 and they called me and said my contract is become to an end, so they offered me another phone and i refused it, so they blocked my both sim card, so is fine but now they keep on calling me that i did not do cancelation so i am owing them R2044, i told them that i am not going to pay that amount because i am done paying my contact.