Treatment was unfair and I was caught under false pretensions

I got a new Samsung galaxy 3 watch after I read on internet that you can connect your contract number to an esim watch. I would like to add that I already have a galaxy 2 watch without the esim, but I would like very much to be able to receive calls on my watch while my phone is maybe on charge at home. After all the money spend I phoned Vodacom to connect my watch to my contract number (because the shop told me customer care must activate it) then and only then I was told that only open contracts can be connected not pre-paid contracts. I was in shock, no one at the shop told me this, I was totally misinformed about this. Why would I spend so much money to get an esim watch to have the same functions I currently have. I was advised by the Vodacom agent that I must change my current contract to an open contract and that it will cost allot more than I'm paying now. I feel I was not treaded fair in this deal. I really need help regarding this issue