fnb connect

Hi I am with FNB bank for some years now and have a couple of sim contracts and devices from them but it's the worst network and customer support I have ever seen I have been reporting tje network and signal problem for over a year and I even reported it at the branch and nothing os happening they say it's my device that means all 5 of them must be faulty please I need help I am planning on canceling all even my bank account