I'm sure you are aware your account with (company) is overdue. Your current balance is $(amount). Please send your minimum payment of $(amount) by (date) to avoid any unnecessary collection fees.
Sincerely,
(your name)
Dear (recipient's name),
I'm sure you are aware your account with (company) is overdue. Your current balance is $(amount). Please send your minimum payment of $(amount) by (date) to avoid any unnecessary collection fees.
Sincerely,
(your name)