I just experienced this and after lots of frustration was able to figure out how it happened and how to fix it (keep reading).
**HOW: **So apparently Google did a deal with Constant Contact which owns Singleplatform.com that allows them to publish edits to ANY local business and they have used this to SPAM entire categories of local businesses by adding in a "Appointments" and/or "Menu" link to the Google My Business listing for search/maps and they have done it in such a way that it is extremely difficult to remove/fix. (NOTE: they are not listed in Google's list of 3rd parties which automatically add info to your listing....https://www.google.com/maps/reserve/partners)
**THE PROBLEM: You have a link to a menu or appointment page that you did not add and can not edit. **The options for setting a URL for "Menu" and/or "Appointment" (and a few others https://support.google.com/business/answer/6218037) are tied to the Primary Category set on your GMB listing and are only available to certain categories.
FIXING: You would think if you are a verified owner of your GMB listing, it would be simple - but Google/SInglePlatform.com have gone to great lengths to make it more difficult....
Step 1 - Make sure you are a verified owner of GMB listing
Step 2 - Change your Primary category on the business to one of the categories which supports the link in question (no definitive list, but I know setting Primary to "Restaurant" will get you Menu and "Interior Designer" will get you an Appointment link)
Step 3 - Save the new category
Step 4 - Now you will have the option under your "URLs" section of GMB listing.
Step 5 - Change the URL from the SPAMMY link to a relevant page you control and Save
Step 6 - Change Primary Category back to what you want.
