What they are trying to do is get you to give them the pin number so they can claim your listing, making them the owner of it.
No way. They will control your account if you do that. Use the code yourself and you will be tho sole owner. Dead easy to do it yourself and it’s FREE !
If you list your business on the actual Google Business page, you will get hard copies of stuff in the mail with codes where they will then ask you to confirm it online. I had 1 call from them (Google actual) and they referenced the stuff I had gotten in the mail from them, along with the sticker for the window of the business.
So for others coming here, Google *may* call you to verify info you’ve entered (like your phone number), but they won’t ask for money nor will they use the shady practices listed above.
Just found out today that my business partner had been dealing with “Google” for approx. two months now and she explained that a “Certified Google Manager” at this company was trying to “get our business on Google” and get us onto the first page of Google search results. My partner had already paid $150 by credit card for “getting our business on Google”. First off, I “got our business on Google” two years ago myself, and pay for a Google Ad monthly. I was suspicious, so my partner gets our so-called Certified Google Manager to call me. My first question was (1) Do you work for Google or some other company A: Some other (marketing) company. Then he explained he had been working with my business partner for 2+ months and that *he/they had 
got our business on Google*. (Outright lie). Then, while on the phone, he searched “our business type” in “our city” and told me how bad our search rank was. I explained to said scammer person that our business is highly location dependent and can only serve a small service area “aka radius” around our operating location. The idea that he thought we needed to be first on “business type” in “our city” showed he had no clue how to market our company. On relevant search terms I have investigated, my company shows up along with only 2 others businesses in a 10 mile radius. Also, we’re on page 1 of search results (and map search results) when a “near me” search or location limited search is performed. We have a number of great Google reviews, and most new customers tell me they “found us on Google”. These guys are out of New York and have a range of hundreds of sequential numbers. Now I’m upset because I tore into my business partner who was only trying to help.
This company did NONE of this – it was already in place
It’s scary how bad they trick you into thinking they work for Google. It’s funny, they makeup the term of “Certified Google Manager” or say they are a “Certified Google My Business Professional”. Neither of those exists. Google offers certification for their AdWords (PPC) and Analytics services but not for Google My Business. I am glad you were able to stop this process before you were scammed.
Educate other business owners and spread the word to help protect others
I have a company that’s called me every day for the last three weeks. I have turned the tables and I continue to harass their representatives every time until they hang up on me. them