There are  two different issues here:1) A repayment agreement or settlement must be mutual: if the company did not accept your payment proposal or agree to it, you cannot unilaterally force  them to accept it. Hence if there was no mutual agreement to a payment plan, they may take your check and continue to proceed against you.2) However,  they can't take your check and ignore it--rather, it must be applied to what  you owe. You should make sure you can prove it was deposited or cashed; if you can do that, you can at least ensure that you are credited for that amount if they sue or take other action.