Why does the Mobile Data on my phone work unstably ?

[Android Central Question]

Hey there, I own a Lenovo A1000. I have been experiencing this strange issue lately with the Mobile Data. When I switch the data 'ON' it works for a few minutes & then suddenly it stops ! The button remains 'ON' but the data doesn't work & it starts working again after a few seconds ! While it doesn't work the data icon on the status bar disappears & then it comes back again !

Is this an issue with my Phone or the Data Provider ?