This is very similar to what just happened to me yesterday.  I called what I thought was Quickbooks from my Iphone contacts (saved from a few months ago), I've been having issues with the Payments feature not woking correctly and nable to take payments from invoiced clients. 

Trusting this person, I gave him access to my MacBook with screen recording, he had me send an invoice to myself to see if he could spot the issue. After he verified that there is an issues, he wanted me to pay to "update" the software and insisted that I couldnt do it. I had been working all day, I was exhausted and clearly didnt have my guard up but I knew this was insane, I kept asking him, why would I need to pay you to fix an issue that is part of the service a pay for every month?

I told him, still thinking I had contacted Quickbbooks that I am going to switchi to another accounting software, he said, what are you going to do about your accounting files, as if to remind me of how frustrating a migration can be.

Finally, shaking, I hung up the phone, shut down my computer, restarted it, deleted the app he had me download, ran a security scan and went to bed.

This morning I called again he told me he would call me back in 30 minutes without getting any info from me then he called from a private line (Los Angeles) about 10 min later and told me it was a scam, gave me QB phone number (which is the same number in my contacts, very frustrating and confusing but at least this person did not try to get my to pay anything and told me that QB does not charge for help and told me to call back on Monday.

I can easliy see how people can be taken advantage of in this way, particularly when small business owners are busy, stressed, tired and just need a solution. Im calling this number on Monday and I hope I get the help I need to simply except payments for finished projects. So frustrating and frightening.