Earlier quoted context omitted.
Even though the SIM was part of the car they bought, the SIM's contract is not in their name which means using the contract would be theft.
Is there case law on this? I don't see any way in which this is legally theft by the OP (admittedly my knowledge is more US-centric than Euro-centric). If I let someone tether a device to my cell phone (or loan my phone to them), are they committing theft? The company on the contract voluntarily gave the SIM to OP.
I may even consider filing against the previous tenants for not removing them and so my being filmed destroying them was without my consent, it’s a clear crime to me to record someone on their private property without their permission ..
This is absolutely not normal anywhere.