Proof of Medical Insurance to enter the Czech Republic

Hi There,

I booked the European Inspiration tour departing April 28th and apparently I need to provide proof of medical insurance to enter the Czech Republic.
I decided not to buy the Contiki Insurance, since I already have a comprehensive medical insurance with worldwide emergency medical coverage.
I didn't actually get a copy of the insurance contract, since this is part of my benefits package at work. The only thing I have is a plastic card, with my personal info, the plan number and the contact numbers.

On my Contiki Invoice, there is a warning message that everyone who does not buy the Contiki insurance will have to provide a copy of their insurance documents to the Czech authorities, prior to crossing the border.

Has anyone who went on a tour to the Czech Republic used your own private insurance instead of the Contiki one?
If so, what did you present to the customs agents when crossing the border? Will the benefits card suffice or you need an actual letter from your insurance company?

Please advise.
Thank you.