pep dont tell you the truth when selling cellphones

Bought a cell phone yesterday dual sim which is mtm on 1st sim was told that we could use vodacom in second sim slot now i get told you cant use the second slot until you have had the phone for 12 months very unfair why have dual sim if you cnt use the second slot I would never have bought the phone had i known this the phone is useless as i need to insert the vodacom sim to access my whattsupps on my old number