Builder increased price after contract signed

[Lin Pan]

I am under contract with DR Horton, the national no.1 builder. They discovered an error in the system that they put in wrong floor plan on my contract and need to update it. Now they are citing the correct floor plan is more expensive and need to increase price by 13k. The lot number and the address is correct. They offer me either cancel the contract get deposit back or sign the addendum with higher price? Can I fight back to ask them to honor the original price? What should I do? Any suggestions?