Ok i am new to android and helping a mate to set his new galaxy core

i can't seem to get on 3G it just show a E while i go online and it's slow

do i need to switch on 3G somewhere or it's the sim card ?

I expect it's just the Sim card or you are in a weak signal/oversubcribed area. In a weak signal/oversubscribed area you can still get slow speed...like Edge speed...even through the little indicator in your status bar may reflect H or H+ making you think you are getting a fast connection. And it's not uncommon that you may have to dial a certain number to activate 3G access for the Sim card; otherwise, it stays set to Edge access speed only. On your phone you only have the choice of turning Mobile Data on or off....since you are getting a slow speed connection it's obviously turned on....you would also most likely get notice your Mobile Data is not turned on anytime you tried to access the internet like using the browser.

Where in Thailand are you located?

Which service provider are you using?

That model has limited 3G frequency capabilities so might match up best (today) with the new AIS 3G/2100 MHz service.

You'll have to match your phone to specific service provider for frequency and coverage, add value, subscribe to a mobile data plan and (possibly) configure an APN.

More details rather than none will likely yield specific recommendations.

I am in Bangkok

not sure do i have to switch the 3G on like the iphone and i can't find the 3G option

i am just on E all the time, might be the sim card need activation