Telkom Annoying service

I got a call from Mondo agent selling me a telkom contract for 10 GB monthly that includes a router. after receiving a router in March i notice that the router had no coverage in my area i called them in April to request a cancellation and they dragged the whole process taking me back and forth it took 6 months Now they said because its been 7 months i have to pay device fee of 1,120 and cancellation fee of 870,02. this is not fare for me because i raised the issue a month after and there are no cancellation fee within 3 months.