Blackberry not working, please help?

[Taylor]

Until two days ago on my Blackberry 9300 I was able to use BBM, Facebook, Twitter and the Blackberry World App Store without being on wifi but now I cannot access any of them (apart from facebook and twitter when i am connected to wifi).
It says i am connected to 3G and I am on tesco mobile and when I am connected to wifi it also has a blackberry logo in that corner, but when wifi is off it vanishes.
I am on a pay monthly Blackberry tariff with Tescos and get 500 mb data per month which i have never reached the limit of so its not that i have ran out of data.
Please help!
Let me know if you need any more details

[Daz]

take your battery out, then your sim, wipe the sim with a cloth then blow in the sim tray then put sim back in then battery wait for it to load up if it continues you will need to ring customer services