You're probably an aspiring actor or model, right? I thought so!
First things first, you've gotta do your homework on any talent service company, even one source talent
You can start by checking out their social media profiles if they are updating them regularly this is a good sign that they care about their clients and want to keep them informed with good information.
Also, what free services do they offer? For example, onesourcetalent.net is a great free resources for talented people to network.
All in all, a little bit of homework, goes a long way, seriously! get your pen and pad, do some homework read reviews and you'll be pleasantly surprised at what you find out about the talent services company you're doing research on.