I had a terrible experience with THLevling. I purchased a gear upgrade from them for one of my characters. I have two accounts (one belongs to my son so we can play together). While my gear was being upgraded (I was asked not to log in so it would not "interfere with the process") I logged in using my son's account and immediately noticed that someone was logged into my bank-alt. THLeveling had no business logging into my bank so I immediately became worried that something was wrong.

I logged in to my account and discovered that all of my gold was gone and most of the items out of my bank had been sold off. I immediately changed my password, submitted a claim to blizzard to get my stuff back and demanded a refund from THLeveling. Not only did they steal my stuff and refuse a refund but they refused to speak with me after I asked for a refund. "We don't give to refunds, we can give you gold tho for your troubles" (misspellings/grammar issues are theirs)

Steer clear of this shady business