The best option for getting a new phone on a preexisitng plan?

[misskay]

Hey everyone!
So I came to fido with my own phone (BYOP) (I brought my iPhone 5s) and was lucky enough to get a great deal with a black friday offer of 3gb for $55 +tx. I really want to be able to keep my plan and upgrade to a 6Splus or 7S plus, but it seems theres no way for me to do this without buying out the phone in full term. Is there not some type of upgrade available to exisiting clients who want a new phone? It seems all the options are the same as a new user would get. The alternative it seems would be to get the phone on 2 year plan, but I would only get 1gb (or 4gb) for $90 which is nearly double the price!! 
Desperately looking for help, or correct me if im wrong!! 
Thanks!

***Edited to add labels***

[KAPABLE-K · Accepted solution]

@misskay if you would like to get a subsidy on a new phone you would have to switch to a plan that allows that. Bring Your Own Phone (BYOP) plans would not qualify for a subsidy on a phone and there is no way around that, unfortunately you would have to switch plans.

Fido always have different promotions so just keep checking the website.