I was told I have excess contribution in my HSA being taxed at extra 6% and I should withdraw before Apr 17, 2018. I don't think that's true. What's wrong here please?

[CarolC]

If you contributed more than allowed you may incur an excess contribution tax:  $3,350 for individual plans or up to $6,750 for family plans.

Also, you must be enrolled in a health insurance plan that imposes high deductibles that meet or exceed IRS required amounts.  See the screenshot attached for the minimum deductibles.  The amounts are the same for 2017.  You need to have the coverage  on the first day of the month in which the contribution was made.

See this TurboTax article What is the IRS Form 8889? for more HSA information.