Product: Mortgage

I purchased a 30-year fixed mortgage in XX/XX/XXXX from XXXX XXXX in XXXX, who sold it immediately to another company, which sold it to another company - Citizens One XXXX  XXXX, which sold it to XXXX XXXX. Citizens One is still the company I make my mortgage payments to. 
In XX/XX/XXXX, I was due to renew my homeowners insurance, but because of a 50 % increase in premiums, I decided to go with another insurance company. The new company offered me a large discount to prepay the insurance, and I did so. I notified Citizens One immediately and told them I would no longer need to have my homeowners insurance escrowed. Citizens One had prepaid the former insurance company a couple of weeks earlier ( XX/XX/XXXX ), so I sent them a check for the amount they had paid, in order to eliminate the hazard escrow. I asked them to recalculate my monthly mortgage payment. Citizens One said my new mortgage payment would be {$800.00} ( a reduction from the {$940.00} I had been paying ). 
My XX/XX/XXXX mortgage statement did not reflect the new payment amount, so I went ahead and paid {$940.00} online. In addition, Citizens One wanted me to pay an additional {$140.00} to them, which they called a hazard escrow waiver. I paid that amount, but do not think I should have had to pay this amount. It's an egregious gouging fee that entirely unnecessary. 
On XX/XX/XXXX, I was going to pay my mortgage payment online, but they still had the old monthly payment due of {$940.00} and there was no way to pay the amount I actually owed - {$800.00}. So I sent them a check, which they cashed. 
In spite of the fact that they cashed my XXXX mortgage payment, they gave me no credit for it. 
Today I got a monthly mortgage statement for {$1900.00} for XXXX - including the old amount of {$950.00} for XXXX, {$950.00} for XXXX plus a late fee, in spite of the fact that I had paid my XXXX mortgage and they had cashed the check. I have no idea what they did with the cash from that check, but they did not apply it to my mortgage. ( A trip to XXXX, perhaps? ; 0 ) ) In addition, I'm getting collection calls from them now. 
I have NEVER in my life had a late mortgage payment. Citizens One Home Loans has offices all over the place - their hazard insurance office is in another state from their payment office, they have divisions in different states for different purposes, and it appears that none of them communicates with the others. 
I have called their customer service people three or four times since XX/XX/XXXX. I have a case number, but no one replies when I try to contact them. I just keep getting collection calls, even though I'm not late on any of my payments. 
The way I see it, they owe me {$140.00} for the amount I paid NOT to have a hazard insurance escrow account, and they owe me {$140.00} for the amount I overpaid in XXXX for my mortgage payment. In addition, they MUST credit my XXXX mortgage payment to my mortgage account. They MUST contact the credit reporting bureaus that I was not late in any of my payments. And they MUST fix my monthly mortgage statements to reflect the proper amount of {$800.00}, instead of the {$940.00} they are still billing me for. I also want their collection department to quit calling, bugging me for payments that are NOT due. 
Is there anything you can do to help? This irresponsible, malign behavior can not be legal, surely. I have always been a responsible homeowner and mortgagee and I am frustrated beyond words. I appreciate any help you can provide.