Along with crypto exchanges and brokerages like Robinhood, some payment services allow users to buy and sell cryptocurrency, although your options for tokens will be more limited, and you usually won't be able to move crypto out of your account and into a private wallet.
Cash App, Venmo and PayPal all let users buy bitcoin via their payment apps. Cash App only buys and sells bitcoin, but it's the only payment service that lets users withdraw crypto to their own private wallets. Crypto fees aren't advertised on Cash App and will vary from trade to trade. Generally, Cash App will charge lower fees than most crypto exchanges for smaller trades, yet higher percentage fees for larger trades.
Venmo and PayPal support bitcoin, bitcoin cash, ethereum and litecoin. Both use a tiered fee structure for crypto that's similar to Coinbase's -- $0.49 to $2.49 on transactions up to $200, a 1.8% fee on transactions between $200 and $1,000 and a 1.5% fee on transactions more than $1,000. Both sites also charge unspecified spread fees that are estimated at 0.5%. You can send crypto to other Venmo or PayPal users with each service, but you can't move your crypto into your own wallet.