so.. to clarify; you want to use a seedbox with a vpn from your smartphone?

if that is the case, you should be able to. The connection depends on the VPN you use.. Assuming you are planning on this type of connection (read below)

phone --> VPN app connection --> seedbox.

if I am correct, then that should be no issue. Nearly all seedboxes allow connection from anywhere, and most vpns will be static IP, but some are dynamic. your seedbox usually is always gong to be a static IP. By that I mean that the IP address assigned to your seedbox will be static (99%) of the time.

I hope this helps.

Cheers,
Buttlove