Greetings!
It's perfectly safe Reza. First of all, we never store your posting keys, meaning that we can't access your funds. We will only use your account to upvote other member's posts.
Secondly, it is not possible to get banned from Hive. Hive is an open network where nobody has the power to delete your account. It is one of the beauties of Hive :)
Thirdly, and most importantly, this service is meant to help small users grow their accounts in the face of larger competition. There is nothing illegal about it and we have had multiple services like this in the past.
Thanks for reading, I hope you will join us. You can ask more questions on our Discord server. We'll be glad to help out.
The Groupvote Team