Don't bank too much on these trade in's. They give you a number when you buy the new phone, but when you actually trade in the old one, they find reasons to whack that number down. You're likely better off selling it on Carousell.
Traded in with fortress, broadway, Wilson etc. before. No issues. You might want to shop around these retailers for their trade in prices ~ some are more generous than others.
Why are those stores paying high prices (more than Apple) for olds phones? Do they resell them?