Need 2 phone lines in my Iphone 15

The majority of iPhones are made IN China.

Presumably you mean made FOR the Chinese Market…

While it doesn’t support eSIMs; it’s still a Dual SIM phone …

… you just use 2x nanoSIMs

Using Dual SIM with two nano-SIM cards - Apple Support

If the device was originally sold in China, it accepts two physical nano-SIMs.

When you say two phone lines......does this mean that you want to use two different carriers?

If yes, you will need to make sure that your current carrier has unlocked the phone, since you will not be able to add service from a second carrier until the phone is unlocked.