Sending in old phone

[Bellamcccc]

I have an iPhone 15 with £300 left to pay, I can get an upgrade for the same amount per month but I will need to send in my current phone (which they estimate the value to be £300). This is based on no water damage etc, what if when they receive my phone they deem it to be worth less? At this point can I cancel the upgrade and get my old phone back? As I understand they send the packaging to send in your old phone with the new one, so should I keep the new one unboxed until my old phone is assessed incase I want to cancel the upgrade? I'm unsure what to do 

[caesarome]

@Bellamcccc 

When you return a device it will be inspected by the company that handles the returns and you will be given a final estimation of it, if at this point you do not agree with this then you can request it is sent back. before sending it off, if you can take some photos to show what condition it is in from all angles including the screen.