Hi to everyone.
I bought my BV9500 in Greece in the first days of February. Everything was fine using my Greek sim card. 
Two days before I came to Qatar and added my local sim. Unfortunately, mobile data is not working now on my BV. I tried the local sim card to another phone and mobile data worked fine. My Greek sim card is working in BV and its mobile data also. 
Because my work, here in Doha, demands to stay online and have access to my email accounts all day via mobile internet, please advise what I should do to solve this issue.
Thanking you in advance, I look forward to your suggestions.

Such issue seems to be related to an incorrect set of APN settings linked to such phone carrier. You should contact the phone carrier, or change it for another one.