Mtn worst service line 135

I upgraded on 8.05.2020. My pocket router is not working correctly. It cant set up of connect to any device. I have tried to contact 135 about 10 times cant get through to technical department. Even the store where I upgraded dies mot contact me back to assist. I am paying for nothing! Call centre cant help and just say call again 135 option 2 then 3. Still no techical department.