Vodacom happily goes on de*****ing their customers

I have 7 sim cards from Vodacom linked to the same acct. One of them is in a tablet that I use at home on my uncapped fiber line, but sometimes I need to access internet through cell network when loadshedding, so I have airtime loaded to convert to data when needed. I have basically paid for that airtime, so why can't I just transfer it to 1 of my other sims in an actual phone when the airtime on that sim is finished? When I requested Vodacom to convert the tablet to a prepaid instead of contract, because of this problem, they told me that it would not be a problem to transfer the airtime. What a bunch of lieing ******* & they've ******* me into another 2 yr contract.