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You should have had the customer sign and date the document. They had no right to cancel the order that you placed. The company that canceled the order (per customers request) may be in default of your order.
Your statement of: "And on the receipt to the customer it says that the money received was going to be used to go towards the purchase of the material." This would imply that you had no other cost other then the material itself. Unless clearly stated on what the full actual total cost would be and signed they may indeed have cause or reason to question what has been done. This does not however on the surface appear to be "money taken under false pretense". But perhaps poor handling of contractual agreements. Let me know if you need further assistance.
Then it would simply appear that they are upset only at your profit mark up margin and there is nothing legally wrong with this. It would be best to have had a signed contract for the job as it appears that they simply went out on their own and priced the product. You have done nothing wrong to be deceptive. You do need to return the money though if your not able to fill the needs of the customer. If the order was placed in your name then you may have legal grounds to file a civil suit against the store. They had no right to tell the customer what your cost of the order was if it was under your name. If it was under their own name then the company can give that out. Again, proper paperwork and details would have helped with this not occurring.
You have not been deceptive unless you gave them a price for cost from the store and the store gave a different cost to the customer. Again, reason for a signed contract. I hope this better helps. Let me know if you need further assistance.