Yes, you should be concerned -- are you sure this "legal company" is a CA licensed law firm? Can you look up any of the people identified as lawyers on the CA State Bar site, www.calbar.org? Lawyers don't charge people to be members of a class, so it sounds like whoever's doing this is really some debt counselling company or something, or is running a scam.
Realize also that successful class actions require the class to be certified by the court, which is difficult because the members need to have the same facts in their situations and the same type of injuries.
I'm only licensed in CA. Please note that this answer does not constitute legal advice, and should not be relied on, since each state has different laws, each situation is fact specific, and it is impossible to evaluate a legal problem without a comprehensive consultation and review of all the facts and documents at issue. This answer does not create an attorney-client relationship.
There is generally no charge for joining a class action lawsuit.
Most lawyers will ask you to sign a retainer agreement that gives them a percentage of your recovery, plus reimbursement for expenses they have incurred on your behalf, or on behalf of everyone involved in the case of a class action.
This sounds like a possible scam, similar to credit repair scams, where a fee is charged upfront for "information" or "access" to something that is otherwise free.
You can find a number of MERS related class actions by using Google. Most are state specific, but you may try contacting some of the lawyers involved in those cases to see if they also have a case pending in California.