Synchrony Bank Credit Card Complaint

Synchrony Bank Credit card department,

Credit line increase/decrease California

I went to Ashley 's Furniture Store in - -, and was told I was approved for up to $7200.00 made an $8000.00 purchase and paid $800.00 cash now the credit card company is saying I was only approved fro $6600.00 and it dropped my credit score by - points because the account shows overdrawn. Please have Ashley 's Credit Department fix this I was lied by them just to get the sale I see this as a Bait and Switch and a UDAAP violation very deceitful. Please Help