I am interested in having a LG Optimus L3 with a monthly fee of 20$ CANADA-WIDE TALK AND TEXT PLAN. Because I don't expect much talking and usage while being in my current wifi area. But can I change my plan whenever I need? e.g. before I go on a trip, I may expect more data usage and want to change into 30$ CANADA-WIDE DATA PLAN. And can I change back into the 20$ plan after that month? Thanks.