Can I change employers while on a Czech Intra-Company Transfer Card?

The ICT Card is purpose-bound: it authorises you to work only for the host entity within the corporate group named in your transfer, for the stated purpose of the transfer. You must keep that employment and keep fulfilling the transfer's purpose throughout your stay.

Moving to an unrelated employer is not what this permit is for and can cause it to lapse. If your career plans change to a normal local job, you would typically need to apply for a different residence/employment permit rather than continue on the ICT Card.