Can a business in another state hold your payment until it's late?

I brought and paid a deposit on a storange bulding in dickson tn from cook storage they hold my payments until they are late they lose my payments then want to charge alot the next month example my payment is 197 they want over 400 for me to keep the bulding in I think March they said they didn't receive my payment so in April I wrote 2 checks and put the late fee on the 1 for March put in the same envolop they cashed the 1 for March 2 weeks after the 1 for April so I started mailing them wit a tracking #so I know when it gets put in their mail box. It always gets their by the 5th but they say they don't get it till after the 6th when it's late now this month their saying they haven't received my payment they the say I owe 2 different amounts 900 and 500 they have cashed the check can they charge a late fee if they don't check their mail til after the 6th if I have a tracking #from the post office saying it was in their box by the 5th