Phrases "withdraw balance" and "deposit balance" are nonsensical in English.

[someonefamous]

'Balance' as a noun is the name of the number representing the amount of money in your account. You cannot withdraw or deposit the actual number. You can however:

• withdraw money
• deposit money
• increase balance (by depositing money)
• decrease balance (by withdrawing money)

I'd just call the two functions withdraw() and deposit(). They're not ambiguous, as there's only one thing you can withdraw/deposit (money).