My advise to you as a Canadian banker for over 30 years and have deal with many more serious fruads.
1) call RCMP and file a formal complaint/investigation
2) go to your bank and request a change of account number or input a "caution " message on ALL your accounts
3) Do not take his call, if you do not have caller ID, hang up and turn off your phone as soon as you recognized his voice. STOP COMMUUNICATION, DON'T BOTHER YELLING AT THIS TYPE OF PEOPLE, WHEN YOU STOP THE COMMUNICATION, THEY WILL STOP.
4) keep his cheque and the envelope as proof of suspected fraudulene attempt in case you have to go to court.
5) do not send him any money, you will never hear the end of it if you do. He will have 10 other of his crime partners to contact you for more.
6) discuss with your cell phone carrier, if you have a police report number, they can give you a new number without charge. It is really a pain in changing phone numbers but it will bring you peace.
This is a classic case of fraud. The cheque is non cashable. What happened is that if you fall into their scam; deposit his cheque into your account and withdrawl funds to give him back his change, you will
say goodbye to $4000.00 of your own money because the cheque will bounce . The bank will take out the funds in your account to recover from their loss. If you don't have the money in the account, you will have an overdraft plus paying overdraft interest of 21%.
If you need my assistance, I would be happy to help out. Rivent has my contact numbers. Please don't be afraid, you have lots of people here willing to help you.
Take care.