SDG Cargo Trailers

I put a deposit down on an 18’ enclosed trailer on 02/04/2022. Balance was $6145. Got a call on Wednesday, July 20, that the trailer was ready. Was told by the owners wife that there was a note on the account that I was going to be charged $500 more due to a material surcharge. I have called at least twice between February and July and not once did they mention this surcharge, even confirmed the original balance due of $6145. The owners wife informed me that I only had an invoice, not a signed contract. This apparently gives them carte blanch to charge whatever made up charges they feel that the customer will pay to get their trailer after waiting on it for months and taking a 5 hour one way drive to pick it up. If you look at the invoices clearly, they have the same invoice number and looks like it was printed on the same date. I have done enough bookkeeping in my days that if I was to look at their software, I would find the auditors trail that would clearly state what date they changed the original invoice. These people are shady, unprofessional and unreliable.