The SoFi Credit Card cannot be used to pay SoFi Student or Personal Loan.
However, you can use the rewards earned from your SoFi Credit Card to pay down your loans, invest, or save. See more details on SoFi Member Rewards Program, here https://support.sofi.com/hc/en-us/articles/360050904672-What-is-the-SoFi-Member-Rewards-program-.