Overcharged for wifi contract

We have had a wifi router with Vodacom probably for about 4 years. This year it was due for an upgrade in March, my husband got a call from Vodacom offering a few packages and he wanted to discuss this with me first. The guy said he would call my husband back which he never did, my husband has a job to do as well and he never got hold of Vodacom. What happened from paying about R279,92 excl VAT a month for a 10gig contract and for us not renewing it, they simply are charging us for the month of April R437,72 excl VAT. Purely because we didn't change our contract. Firstly it's a wifi router, our Vodacom App has never notified me ever of any upgrades due. Because it's a Router and not a phone we therefore are not aware of what is going on as it's something that is not in physical use in our hands daily. I have been a Vodacom customer for probably over 14 years, anytime I didn't upgrade immediately my existing contract would roll over on a month to month basis until I found the deal/package that suited my interests. I am wanting Vodacom to reverse this fee, I am not getting a 20gig contract for R299 after my husband sorted this out with them on the Easter Weekend, so I'm getting more for less so how the heck do you justify charging me more for 10gigs. I am sick and tired of the high fees we pay, always running out of data and trying to stay awake later on weekends so we can use the midnight owl bundle.