Vodacom - Mondo service providers are **********

I won a dispute of a contract migration where Vodacom a third party company Mondo and I was expecting to be refunded my extra amounts and this was in January, after calling them constantly Vodacom who don’t want to take responsibility but would put the blame to Mondo as it’s their service provider. I received an email that they will credit me April and May of which I fail to understand I made it clear that they should credit me from December 2021 to date as the fault is with them by implementing a contract of what I didn’t want