Bad service from Vodacom store

I bought a phone for cash at vodacom southgate on the 24th of September and asked them if I can use any other network for internet because its dual sim phone. They said yes it allows all networks, surprisingly when i get home it only allows vodacom sim for data. Took the phone back on Saturday they said people who can assist works Monday to Friday. Went back yesterday Monday the 27th thwy took the phone and said they returning it thwy will call me after 7 days. I paid my money and I have no phone as we speak what happened to the fact that you can return the phone within 7 days to get a different phone if thw onw you have has issues or you get refund if you cant be given an alternative. I mean why should I suffer for their own problem. This is very bad service and taking advantage of consumers.