I have paid my bill on time every month. Set up a ...

I have paid my bill on time every month. Set up a automatic payment. I talked to them and ask if all my bills could be put into one balance and they said yes we will do so. I have never missed a payment but now they are sending me to collections. For a charge that they forgot to put on my balance and they will not add it to my balance. They said I can deal with the third party and pay them. Cox financial departments are the worst i never have any trouble with Mercy and there financial department.