I don't have a microphone, is phones microphone alright?
Honestly the answer is no, or at least highly unlikely.
Most of the voiceover artists here that book work have a professional setup and a quality mixing station. A phone doesn't have the dynamic range to do this.
You can purchase decent condenser mics nowadays that don't break the bank, but whenever I hear someone ask the mic question my response is:
Look on TV or in any Professional Studio: How many phone mics or USB mics do you see?
The answer is none.
You need an XLR Connected Large Diaphragm Condenser Mic to be able to be work in 99.9% of cases.