I was planning to switch to ATT from Verizon, but I have preordered 512 max from Apple on IUP today for launch day delivery. If I switch to ATT before new iPhone arrives, any idea if I will face any issues in activation of service ? I think if I switch to ATT before new phone arrives, I just need to pop ATT sim to new phone and be good. Any idea if I should switch after new phone goes PFS ?