You should also contact your Medicare Part D plan's Member Services department and get a corrected Medicare Part D Member ID issued.
Can't find your new Medicare plan's Contact Information?
If you cannot find the telephone number for your Medicare plan, we have most Medicare plan Member Services numbers available through our PDP-Finder.com/FL and MA-Finder.com/15202 tools. You can just look up your Medicare plan name, click on the plan name or the "Benefits and Contact Info" button to see the Member or Customer Services number for your plan.

If you are having trouble getting the misspelling corrected, you can also telephone Medicare at 1-800-633-4227 and ask a Medicare representative for assistance.
Related question: I enrolled into a new Medicare Part D plan and still have not received my Member ID card (and I need prescriptions now). What should I do? See our Frequently Asked Question on this site