It really depends on the situation. If you're in a safe place, have the right tools, and know how to change a tyre, doing it yourself is an option. However, many flat tyres happen on busy roads, highways, or at night, where changing a tyre can be risky.
In those cases, a roadside tyre replacement service is usually the safer choice. A technician can arrive with the proper equipment, replace the damaged tyre or fit your spare, and make sure everything is secure before you continue driving. This also saves time if you're unsure about the process or don't have the necessary tools.
I've found that having the contact details of a reliable mobile tyre service can be helpful for unexpected situations. If you're in Sydney, Back2RoadTyres is one of the services that offers roadside tyre assistance, but the most important thing is choosing a provider that responds quickly and puts safety first.