There are also trustless ways to do that. Bitcoin's Lightning Network does exactly this in trustless way, and it's feeless, instant and private. Every "Lightning bitcoin" is cryptographically backed by real bitcoin. In the end, all transactions are settled on the Bitcoin main chain.
Then there are centralized credit networks backed by Bitcoin. Paypal and Visa (with a custodian / bank) already provide this, in combination with a seamless exchange to local currency that is accepted by the merchant. For custodians, it's possible to algorithmically prove reserves, so that every user can verify that their "bitcoin IOU" is backed by actual bitcoin, but no one currently provides this afaik.
Then there are centralized credit networks backed by Bitcoin. Paypal and Visa (with a custodian / bank) already provide this, in combination with a seamless exchange to local currency that is accepted by the merchant. For custodians, it's possible to algorithmically prove reserves, so that every user can verify that their "bitcoin IOU" is backed by actual bitcoin, but no one currently provides this afaik.