Sim card problems with Blue Label Connect!!

We have a contract with Blue Label Connect, this year we started having problems with the device (Cubot J5) the battery was overheating, around the 3rd of February 2021 they came and took the device, we handed them the device with a simcard in the phone, when they returned the phone the Sim card was no longer in there, we tried calling them with no assistance, today we called again and spoke to an agent who said we must pay R130 for the Sim card he admitted that they must have took the Sim card during repairs, to us it seems like we have a contact within a contract because the Cell C simcard was part of the package we pay 299, we are NOT Happy about this as we feel that we're being ****med by Blue Label Connect