Story time... Back in the mid 90s, I got a late fee on a credit card payment. Well crap, I guess I just wasn't sending the check soon enough. Next month I sent it a little earlier. Another late fee. Crap. Ok, this month I'll send it even earlier! Another late fee. This went on for months and months. It got to the point that I was sending it 4 weeks before it was due, and it would always post a day or two AFTER the due date. Well fuck me. I had no doubt these pricks were holding my payment just to soak me with fees. I couldn't afford to pay if off and close it just yet, so I decided to get quicken and pay for an electronic payment service (I forget the name, but it is trivial now days as most banks support it out of the box). The next month comes, and I send the payment to arrive the day before it is due. True to form, they credit me the day after. I call the payment service, and they go to bat for me, providing proof that the payment was electronically transferred before the due date. They reversed the charge ($25 maybe?). The next month, same thing. After providing proof, they reverse the charge. Same thing next month. Then finally in the 4th month, they credited it on the day it was received! Glory be! I can only assume they set a flag on the account because they never again tried to fuck me that way. This check payment service and quicken paid for itself almost immediately. As soon as I paid off the card, I closed the account and will never do business with them again.

Morel of the story is use electronic transfers so you have proof they got it. Then you have the proof needed so they can't fuck you over. Otherwise, some of those pricks will do everything they can to suck you dry.