Right now I have an iphone 5 that I bought outright when I joined Koodo over 3 years ago. The screen recently broke and I'd like to purchase an iphone 6s or 6s plus. If I purchased an unlocked iphone from the apple store, can I just switch out the sim card and continue with my month-to-month plan? It's a friends and family plan that was a really great deal so I wouldn't want to change the plan. Are there any additional charges that I might face?