Serious Problem

So I had my laptop serviced awhile ago, and today I was contacted by "Dell" by phone asking me about it. The man on the phone said to close my ticket he had to run a few diagnostics and wanted to use the remote connect program that Dell support technicians use to work on your computer. I was a bit skeptical, so I asked him to prove that he worked for Dell. To this he replied with my laptop service record, my serial number, and my warrantee information. It all checked out so I thought it was legit. Then he encrypted my computer and wanted to charge me 200$  for "Anti-virus" software before he would unlock it. I refused and hung up, now aware that it was a scam but the damage was done. 

My problem isn't the ransomware now on my laptop, it was backed up and is getting re-imaged to fix it. My problem is with Dell. How did these scammers get all of this information like the service record and serial number and warrantee information? Either all of this information is given out by Dell or Dell has a serious problem with security on customer information.  If these scammers had my Dell information, the probably have a lot more peoples.