Bad Service network disconnected

I dont like what happens with regards to my contract. I bought my wife a cell phone and sim card has been dissconnected. Last month she thought this is just an error changed the sim to my phone and still the sim card is not working, I called the call centre and my call was disconnected over the wkend. Please advice as what need to happen. Im really sick of this as she cant do anything. this is two weeks. I wont pay for any sim swap as this is the fault of the operator not her fault.