Does anyone know what the law is in SD about writing Paid in Full on your check when paying a credit card bill

I know in some states that if the company cashes it, that is final and there is nothing they can do about it. The reason I'm asking is because I got caught up in a subprime credit card that has all these fees. I know that legally I only have to pay for my charges which will probably show up as a settlement on my report. Any thoughts?