Jerold Kaplan Law Office PC Entred a judgement against me AFTER I made payment arrangements and they cashed the first check Phoenix, Arizona

This company has been relentless in pursuing me for a debt that is old, and they served me legal papers at work. I called and talked with Jennifer, and I asked her if we could make payment arrangements to settle the debt in return for them dropping the case. She agreed and I asked her to e-mail me something in writing. Needless to say, that never happened. I sent her a fax outlining our conversation and sent the first payment as agreed. It was cashed....THEN, yesterday, I get a "notice of intent to seek entry of default and judgment by default"!! I called immediately and got voicemail. I called back and it went to a general mailbox. It is virtually impossible to get anyone on the phone there and you cannot trust what they say. I don't know what recourse I have.