I have never had an issue with either and they are one of my go to MSCs.
While I agree last names seem a bit overkill, especially when only a few people work in a location, it is stated in the requirements.
I have had to get creative to get names of associates of their electronic's company client, as these employees never wear name tags and they require first and last name. They don't like to do quotes for small items in most departments and do not have buisiness cards. I had one associate I sent on a wild goose chase so I could pick up the name tag on the desk, read the long unspellable name, grab a picture to ensure I got it right or else...
Otherwise, I have never had an issue with Service Check and find Karin to be responsive, helpful and reasonable.
They pay on time, have generous bonuses and have been reasonable and responsive everytime I have contacted them.