Unfortunately, you cannot force the police or prosecutor's office to pursue charges because it is within their discretion to make those decisions. You can try to escalate your complaint with the county's attorney's office to a supervisor or higher up in an attempt to get them to pursue your case, but they pretty much have the final word on whether or not to prosecute a case.
If they still refuse, you can still try to sue them in civil court to recover the money. Because the amount exceeds $2500, you cannot use small claims
court. You can either retain a lawyer to help file the lawsuit, or you can try to do it yourself. The Arizona courts have a part of their website that contains the forms you will need as well as instructions. There are different forms for cases under $10,000 and over $10,000 so make sure you select the right ones. You will also want to get your evidence together...copies of the invoices, the checks that were stopped, as well as proof that you gave them a refund for some of the items, etc.
Sorry I can't give you better news about the criminal side but unfortunately no one can really force a prosecutor to pursue a case because they are given discretion in the matter. It may be worth a chance to try to speak with a supervisor or higher up but if you can't get movement in that area you still have the civil option to pursue.