The only way to trust a company you have not had any dealings with is through the kind of reputation they have out there, this can be gotten mostly from reviews of satisfied customers who are willing to recommend the company to others, this is especially so for wallet recovery company since no one wants to hand over their wallets to complete strangers they can't trust and with scammers everywhere themselves days it is understandable that some people are weary about some of the companies online.
Most times, reviews from the public domain as such holds no water but in a community like bitcointalk forum where people of like minds exist can be guaranteed when the trust is gained, and before that happens, you are sure you merited the trust and reviews from a genuine source who has used your services on the platform and they can confidently vouch for you without any fear or favour from anybody not public where reviews can be easily paid for tricking the masses to believe what isn't genuine.