Hi,
First of all, let me apologize for the late response, we are currently under a great load of work and there is delay on our responses.
I made some test with NTAG I2C, and its correct what you did. You can change the I2C address.
I read the memory from the device, with the original 0x55 address, and I received values from the 0x00 memory address.

Then I changed the I2C address to 0x00, same as you. And again read the same memory register, and I received the same values.

The issue could be when you write to the User Memory. Please make sure the host it is doing correctly.
You can try using the Peek and Poke tool if desired to make sure that you are writing the correct address.
Best Regards,
Ricardo