It's a great app...if you read the description. – 來電管家 Call Guard Review

Dear Mrs. Kaveo, I am from the US. I have a US based iTunes. This is why they allow it to be downloaded from the US store. Please stop being rude to your fellow citizens. People that do not live in HK and don't have an account with Smartone-HK should really stop rating this so badly. In fact stop downloading it if you don't have an account! Everyone should know by now it's useless unless you have a plan with Smartone-HK!!! Don't be surprised when it does nothing if you don't have the plan. It clearly says you need to have an account to use it. If you had an account you'd see that it works. If you are too narrow minded to read the description then there is little hope for you (mrs. Kaveo seems to be hurt detrimentally by this.) It works beautifully though. Stops all the banks and insurers with their lame marketing calls + you can block people that block their caller ID.
Review by Smartone user on 來電管家 Call Guard.