Waste Management

I have had Waste Management Service for years. A couple of weeks ago, I realized my garbage had not been picked up for 2 weeks. I called to ck on the problem. Apparently I owed them $206.02. Why? I pay them every month $45. Payments have been coming out of my cking acct every month for the last year and 1/2. I pd a lump sum of $161 to clear the acct. I was told they would do a courteous pick up for the garbage. Didn't happen. I looked back at cking acct. I have pd them $967.02 since Nov 2018 (19 months). Now they say I owe them another $49.06. They cannot explain it to me. They are charging me an average of $52 a month for garbage that I only put out every 2 weeks