I'm going to be brief and to the point.
If you want to use an employment agency, that fails to return emails and calls, pick and choose when they collaborate with you, then Kelly Services are for you!
When they do choose to email you, do not be surprised to find the use of 'text' (or should I say 'txt') speak, short, rude answers and general lack of enthusiasm.
I have made the mistake of twice applying for work through this agency, and on both occasions they failed to act as an agency should. If not found to be 100% suitable, or there is another complication they really will treat you badly.
I have no doubt that they do have success stories or else they would not still be in business, but rest assured I would never use or recommend them. However, generally I would not touch ANY agency with a 10ft pole.
You have been warned.