You document every communication about this that you've had with them. If you didn't document previous communications, you retroactively do so (cell phone record, emails, lists with dates and actions taken).
You send a certified letter, spelling our all of your prior attempts to collect in a list form (you should attach these to the letter) and you set out dates and deadlines that have passed, your new deadline for taking action, and you spell out what actions you will take (e.g. if you do not respond to work out a payment plan within 10 days of receipt of this letter (which you'll know because you'll get delivery confirmation) I will file in Alexandria City XYZ Court, for the amount of ABC + late fees + postage + attorney fees). Then you stick to that. Do you have a lawyer, or an experienced friend who can help you write a letter? My DH is a lawyer and has done this for me, quite successfully, twice.
Make it as easy for them to pay as possible. Reduce the amount owed to $4,500. Give them access to a paypal account they can deposit it into with a credit card if you usually take checks.
No idea about Alexandria's small claims limitations and reducing the amount solely in order to be eligible for small claims.
--Been there, it sucks.