Billed for a month I didn't have internet access on

I am being billed for a month I did not use as they blocked my access to the internet since the payment did not go through. The issue now is that they are saying they bill in arrears , how when the contract is month to month. I paid for rain first before they connected me the first time around.. And they stopped the internet connection as soon as the payment didn't go through. I am being told that I owe them, but how ? Guys please save yourself the trouble and look for a better internet service provider