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SUS no longer works, also re-download the APN settings
settings > more > internet settings > accept
How old is your micro SIM card? do you have any antivirus? also contact your network carrier as this could be a poor network coverage
Is your phone compatible with your network's 3G frequencies?
Have you flashed any other firmware?
3G 850 / 900 / 1700 / 1900 / 2100 - C5302
which carrier/network do you have? because your SIM card might work on other phones that are compatible with your carrier's 3G bands but perhaps your SP it is NOT compatible.
no actually i dont have any idea about flashing with any other firmware ...if i would had i would have rather go with cyanogen mod 
also as you can see in my previous replies i have mentioned that my sim card when inserted in my friends phone 3G works on it.
Again, if the SIM card works on other phones that could be because those other phones are compatible with that network's 3G frequencies, who is network/carrier ? which country?