Network speeds - hidden tweaks in phone?

I have 2 phones on my account. My main one is a Sony Xperia Z C6616 I unlocked from Bell. I cannot seem to get more than 3-4MB download speeds on a good day on it, and most days are bad. Esp downtown Ottawa. Yesterday I upgraded the second phone to an Xperia XA1. Did a speed test with both (after ensuring the APNs were up to date) - C6616: 4 down, 1 up. XA1: ~25 down, ~10 up. That's a HUGE difference. PLease note LTE is not active yet. While I will be upgrading to a newer phone on my main line in the coming months, is there any other settings I can tweak to get my C6616 speeds higher? Like in those service menus? Or is the XA1 getting better speeds cuz it's newer/can use more bands/something like that?