Cost of (Just) 10 days Early Termination

Hello,

I have a contract with ben SIM + phone. However, I already paid the cost of the phone completely. My contracts runs until 21 December 2022. However, due to a good offer by another SIM provider, is it possible to terminate my contract just 10-11 days before its final date?

This is because the offer I mention is only available for orders before August 14. So I want to make the end date of my contract in 4 months from August 12-13. And what will be the cost of doing this?

Thanks a lot in advance!