Unfair billing

Im on a price lock and im paying R474 per month. I missed my payment on the 25th and they blocked my services now I want to make a payment now and they say I must pay R568.67. When I ask why they cannot answer me. The 1st consultant that i spoke to her name is Hlobisile Ndlovu put me on hold for over 20mins i end up hang up because there was no response from her and I was on call with her for over 30mins. The 2nd consultant I forgot her name she just hang up. So I can't make payments that I don't know where the money is coming from and the consultant does not want to assist me with this issue.