If they don't pay you in the next week or two, you may have to sue them. Contact a plaintiff's civil attorney to assist you with this.
THESE COMMENTS ARE NOT LEGAL ADVICE. They are provided for informational purposes only. Actual legal advice can only be provided after consultation by an attorney licensed in your jurisdiction. Answering this question does not create an attorney-client relationship or otherwise require further consultation.
For your last paycheck, do not call send a letter demanding your unpaid wages. In your letter express the exact amount owed or at least which weeks you have not been paid. In the letter, document your attempts to contact them by telephone. Include the dates, times, and whaterver information you can remember. Also, you need to give them a deadline of at least 10 business days to correct the unpaid wages violations.
Make sure your former employer has your correct mailing address. Send the letter by certified mail and keep a copy.
If you still do not have your last paycheck after the deadline, you should file a claim in small claims court for the unpaid wages, attorney's fess, expenses and court cost.
Contact an employment attorney if you need any assistance with the letter or the small claims case.