Yes, if you turn on Auto Recharge on the SMS credits page. Set a "When balance is below ($)" threshold and pick a refill amount from the preset packs (50/75/100/250/350/500). The page describes this as a daily check, but in practice it's checked every time your outbound text automations run — which, on a busy account, is far more often than once a day.

Each time it checks, if your balance is below your threshold, Sprwt automatically charges the card on file for the refill amount plus a 3.5% processing fee, then credits just the refill amount (not the fee) to your balance. If the charge fails, nothing is credited, and it simply tries again on the next check. You can also buy credits manually on the same page (minimum $50, same 3.5% fee) without turning on auto-recharge at all.