Truworths misleading phone sales

Truworths, please advise why your cellphones are locked to the mtn network. I went to purchase a dual sim phone today and was told that the 1sim slot is locked to the mtn network, the sales consultant advised unfortunately that is policy and another network sim cannot be used. Unfortunately I live in an area that doesnt get great reception on the mtn network. Is that not false advertising on your behalf as my hubby received an SMS stating the phone in question was now available at all stores and the advert states dual sim. Nothing about it being mtn locked. Additionally the price of the phone differed from the SMS price to the store.