How and where Canadians are usually buying new phones? As I know here are two ways: buy it in the internet provider (ex. Rogers, Bell, Freedom) with Trade up or Mytub options and monthly payments. Or buying phone in the actual store (Apple, Samsung) with monthly payments as well.

What are the pros and cons of each way?

(Help with buying new device) What was your experience like purchasing a device from Amazon?

I purchased one before and I had some technical difficulties with it, and since then I've been on the fence about buying another device from there.

How do I determine whether or not a seller like "Mobiles International" or whatever random company is legit or not? Most of the reviews are positive but the negative reviews are always something extreme like the device came from Vietnam and wasn't unlocked as advertised, or it just decided to malfunction after a couple of months of use, or the scary part it just didn't show up at all and they never got a refund (no update was posted on whether or not they got a refund I just assume the worse).

Is it just a risk you have to take? The specific device I'm looking for is a 256 8gb Light blue Galaxy A15, but the only "safe" sellers (Amazon) that have it only have the standard 128gb 4g or 6gb models.

I just want to put my mind at ease. I would normally do in store (Metro by T-Mobile) but they only have the 64gb version (didn't even know that was a thing) so that's not really an option for me either.