In the UK if you are using pay-as-you go accounts you would say "I need to top-up my account / phone / balance". Top up = to add more to something

Hi Sasha. Usually, at least in the U.S., we don't refill or recharge cell phone accounts. Most of us have a monthly cell phone bill, so we say, "I need to pay my bill."

DavidK's answers all sound good to me. If it's a prepaid phone card, you could also say "I need to add money to my card" or "I need to refill my card." As others have said, most people in the US don't use prepaid accounts for phone service, but there are some similar kinds of prepaid accounts that we do use, like prepaid gift cards (a lot of these can be refilled), or even websites like Italki where you have to add money to your account if you want to pay for lessons. Also, before cell phones became popular, there were prepaid phone cards in the US that you could use to pay for long-distance calls.

I need to add minutes/time/money to my account. My phone's nearly out of minutes. I think you can use 'refill' here for phones too. For example, we pay tolls automatically out of a prepaid account, and you can set the dollar amount when it automatically 'refills' by deducting money from you bank account.

Something like, "I need to add credit to my account," although like somebody else said, it's not so common to use that method here.