Trust me, no legitimate mystery shopping company is depositing $600 in people's accounts in advance or sending them $600 checks in advance. The checks are sent by scammers and the checks look legitimate and seem to come from a real company. The bank gives credit the next day, but a week or two later the check bounces. This has been going on for years. From your description, it appears that they are now depositing money directly in bank accounts, but I am sure that a few days later, the deposit will be reversed after you have done something with $500 of the money like buying gift cards and sending them the codes or wiring the money via Western Union. The bank will then want the ENTIRE $600 back from you. This is a SCAM.
You may have responded to some sort of email from a company impersonating a real Mystery Shopping Company and given them your banking information. That is unfortunate, but until you actually use that money, you are alright. Report them to the police. If you responded to something you receive by paper mail, contact the US Postal Inspectors. Banking regulators will want to find them if they are sending bogus wire transfers.
Shopping Southeast Pennsylvania, Delaware above the canal, and South Jersey since 2008
Post removed for violation of Posting Guidelines, naming client and MSC in the same post/thread. Feel free to edit, removing the violation, then repost. Thank you.