Under the Uniform Interstate Family Support Act, a federal act that governs both child and spousal support, the issuing court's order remains in effect until modified, and can be enforced by that state, or another state's, support collection services.
That act is here: http://www.ncsea.org/wp-content/uploads/2012/02/UIFSA_2001.pdf
Most courts will not agree to a modification of support, even if there is a verbal agreement modifying the amount, because the court tends to be reluctant to modify court orders prior to the date of the filing for the request for modification (this is unfortunate because most people assume an agreement between the parties is sufficient in and of itself).
It is also possible to negotiate the arrears; the agency that is garnishing the support would have information on this, as each department has a different program available, with different requirements.
I'm sure this is not what you wanted to hear; but I have a duty to report accurate information. Since the law is always evolving, one may wish to hire an attorney to present the case to the judge to show the inequity of having a verbal agreement and then attempting to "reinstate" a court order; but again, most judges will not entertain that argument.