6 years of payment for faulty device yet expected to pay more to fix it

I got my cartrack since 2019. Assuming its working properly until i had issues with the battery and got no communication with the tracker. When i notify them. They say the will send a technician to check it. Technician came and told me that the device was faulty and they replaced it. 2 days later i am getting more than 10 calls a day between 7 am to 6pm requesting a payment for the replaced device that i did not ask for. The agent did not communicate with me that i need to pay for checking of device, I was not given an option to choose to get it repaired or replaced. they just issued me with an invoice. I have been paying for the service that does not work and expected to pay more to fix it. Had i been told that its my responsibility to fix it i would have taken my business somewhere. Please rectify this or come take your device and terminate my contract.