Netstar not responding and I cannot get hold of them.

I no longer need the Netstar on two vehicles as I have given them to family as we have left the country. I have sent several emails over several weeks and have tried to call multiple times but they never answer. Not sure what is going on but this is crazy.

It looks like the only way to stop payment is to advise my bank that the payments are now ******* and to stop them. What do I need to do to get Netstar to respond and stop monitoring the vehicles and to stop taking payments?