Assist me please

I got a deal for 2 iPhone 14 at R1200 per month including data and minutes on both lines. Later when my invoice appeared on my account, it had shown both lines allocations were billed separately resulting increase to my payment. Each month my monthly instalment was increasing at first was R15 later up to R300. When I had filed a complaint with Vodacom they referred to yearly increase that every other consumer of theirs this has occurred. I let it slide, then came immigration that I had not signed yet they charged me for the data I hadn’t asked for. I asked to do a premature calculation with them my quotes amounted to R23 326.90, I paid on the 30th of April. Received notification saying my lines were prepaid now, when I asked for settlement letter, I was later told I’m still owing R3006.09, as there was a glitch that occurred, I have been calling all departments at Vodacom and going to in store where I took my phones yet I have found no resolution. How can I owe more whereas I paid the amount stated on the quote? I have logged service requests yet no response has been received! For the past 2 weeks!