Useless billing department

Rain has billed me for 7 routers and will not pass a credit and no one in the billing department wants or feel the need to contact me. I have been phoning and escalating this problem since 1st of May when they invoiced me for 5 routers then instead of giving me the credit for the promotion on the first month free they went and invoiced me for another 2 routers and now I can simply not get a hold of anyone that is able to assist me with this problem I should have been billed for 1 router and ended up being billed for 7 routers maybe I will just cancel the service as it is bad service anyways promise to call me within the same day but no one calls and the billing department on the contact number is unable to assist so why they even have that option is definitely a waste of time I have wasted so much airtime sitting hours on the phone with billing departments that are unable to assist I asked to speak to the manager and even that is impossible how do this company operate if they don't care about their clients