To Repay
To Refund, To Reimburse
transitive verb, godan verb
払い is a "payment" and 戻す is "to return." If you return a payment, you are going to repay, to refund, or to reimburse someone for their payment.
The readings come from 払い and 戻す.
すみません、もう不要になったのでSuicaを払い戻したいのですが...。
Excuse me, I'd like to refund my Suica because I no longer need it...
出張中に食べた焼肉代も払い戻すことはできますか。
Can I get reimbursed for the Korean barbecue I ate during my business trip?
恐れ入りますが、お客様は鍵を失くされたので、保証金の払い戻しは出来かねます。
I’m afraid that we cannot refund your deposit since you lost the key.