unfair cancellation

so utterly disappointed .. my gap cover was cancelled without notifying me of a missed payment and possible cancellation. I was not aware of missed premiums due to bank account issues as advised. . after they received premiums religiously , no contact was made with me and the policy was just cancelled. they refuse to do the right thing and reinstate me. I called last week to inquire and received no feedback.. called today and was asked to send a complaint. .no assistance was received hours later???? can someone offer appropriate assistance.