Not in the app. Contact your club to change your partner, leave a league or ask about a refund.
What the club can do
Change a player in your team.
Remove your team before the club has set up the divisions. Paid shares are then refunded in full automatically, and unpaid shares are cancelled.
Good to know
To leave a league waitlist, ask the club.
To cancel a booked league match, open it and tap Cancel before it starts. If you booked it, the match goes back to needing scheduling.