internet access in korea

someone please tell me how to acces the internet in korea using your own tablet/phone..

I will have my vacation to korea next week and i will stay there for about 2 weeks..

the problem is, this is my first time travel to korea and i need to use internet for work purposes and personal matter..

I know there will be a place like cyber cafe and wifi where i can use it but how can i use the internet when i travel in car or the places i go do not have internet connection?

Can someone tell me is there any telecomunication company in korea who have the service for internet using for one day or one week??

Cos in my country, people just need to buy a sim card which is available anywhere to make a phonecall and at the same time they also can use internet for 1 hour, 1 day or 1 month with it..

Anyone please help me..