Pep stores Athlone

About 7 days ago I bought a cellphone at Pep stores in Athlone,they only had Vodacom and MTN ,I had asked them to triple check that the cellphone Is not network locked ,I continued with purchase as they had said it's not I then insert my aim in the second slot also the girl that activated my phone brings it to me in the box doesn't open or turn it on for me to see that intact it's working anyway I had to do all of that I asked her about procedure she rather tells me that the cashier didn't do her job ,so my sim is in I also said there is no ways that I will change from Telkom ,a couple of days later I get a message from Vodacom telling me I need to get a unlock code and that my Telkom will only be working for phone calls remembering it was working for those couple of days on Telkom data and not Vodacom ,I'm stuck now I'm not receiving even sms on my Telkom SIM card , Vodacom has said the device needs to be taken back and that they did not explain it properly I'm so irrateted as I even went to check for another phone at another shop and ended up coming back asking more than one person to double check it ,this was last Saturday but the service I got at Pep Athlone was very never minded this is costing me money now as someone didn't do there job I'm also loading money as this is my business number