The fuse is a safety device that is protecting the wiring from burning up. It is blowing because the charger/phone is pulling to much amperage. Changing the socket to a USB port may or may not fix the issue. By changing the socket, you will have changed the charger or added another adapter to the charger, which could reduce the amp draw and thus stop the fuse from blowing, or it may not. It will also increase the amount of time it takes to charge the cell phone. To blow the 15amp fuse, I would say try a different charger. Do not use a fast or rapid charger in a car. Your battery or phone may be going bad too.
As to changing the socket to a USB port. The car socket voltage varies from ~12.0 to ~14.5 volts. A USB port is designed for ~5.0 volts. You would need a USB adapter, not just a socket, to switch the car voltage to the USB voltage. The adapter will have the instructions for the wiring. You need to know the power draw in watts or amps of your charger so that you buy an adapter that is rated to handle the load. If the adapter is rated for to small of a load, it will burn up or the fuse will once again be blowing. By changing the socket, you have not addressed the problem, which is to much power being pulled by the charger/phone for the circuit it is connected too .
Here is link to an adapter:
https://www.newegg.com/Product/Product. ... -_-Product
power rated for 15Watts. You can use Google to convert Watts <> Amps, figuring the car voltage is 13.5 volts.
More adapters:
https://www.newegg.com/Product/ProductL ... Submit=ENE
And I am sure Amazon has lots of adapters too. Here is link to them:
https://www.amazon.com/usb-car-adapter/ ... %20adapter
Here is one that would be east to install:
https://www.amazon.com/Ginsco-Charger-S ... ar+adapter
Note that it is fused at 10 amps and you are already blowing a 15 amp fuse so this is not going work with your charger.