Looking for a wee bit of advice. I was interviewed last week and gave a figure I thought was my salary when asked what I currently earn

On a call today confirming they would be offering me the position they stated my salary would be exactly the amount I'd originally stated.

Turns out I actually earn 3/4k more. Has anyone had experience of being this stupid and having to deal with this situation?

I'm going to contact the company tomorrow but got a feeling I might now lose out on the job as I can't take that level of pay cut