Mysql problems in shared hosting



Hello everyone and sorry for my English language level.

The problem is this, I'm trying to install OC on a shared HostGator hosting, but can not use mysql because when I enter my username for example: "arthur" (for that was created from the cpanel and it works perfectly with other applications) at the time of installation adds the suffix @localhost then throws me error since the arthur @ localhost user does not exist

How I can prevent not add suffix @localhost?

thank you very much