3rd parties can and do help people recover money lost to scam brokers.
A retainer fee should be standard for these companies since any recovered funds in these cases always go directly to the purchaser and not to any 3rd party.
These are tough cases, as banks will commonly not have trained their employees - even their "Dispute Experts" in this area of chargebacks.
The first point to consider when communicating your issue to the bank is that this is an authorized charge - for this reason the issuer - the bank will get confused if you call it "fraud."
(Fraud to bank agents refers to unauthorized charges or counterfeit cards and the like).
You have a "service-related" chargeback on your hands with the reason being "Not as Described." Visa has the advantage in these cases, with their sub-category "Misrepresentation."
Your best bet is to examine the entire situation, the parameters of the services that you were expecting to receive (expressed and implied - ie in website content), what was provided, who provided it (are they qualified - authorized aka able to have provided the services that they claim to have provided...
Then build your case, gathering evidence of the above and present it to your issuer (usually the bank).
A proper fund recovery company will also provide communication and negotiation services, and will represent their client and their case to bank agents.
Doing all of the above - including showing proper communication and negotiation efforts with the broker - properly will cost you many hours of learning and work.
This is what people pay for when they enlist a reputable recovery company. There aren't guarantees of getting your money back, but in tough cases some chance can be better than no chance.
There is a chance you'll be successful with working your own chargeback, but practically speaking there's a very small chance of success trying it on your own.
This said, you should thoroughly vett any company you work with, checking out their registrations and any licences they're supposed to have. If they're in a random place like Belize or the Marshall Islands (among others) it's an automatic bad sign as these are places that don't have strong consumer protection regs in place, so it's easier for scammers to get away with their crimes by being registered in these places.
One last note is that you may still be able to work a chargeback. You would have a max potential of 540 days from payment dates to raise chargeback claims, though it has to be within 120 days of cancelling the faulty services.