And that's the thing, they use characters when they have to write it, but even then native speakers struggle to read it because there's no commonly used standard way to do it. In practice, they just write in mandarin.
I call them dialects for lack of a better word. For example, an Algerian Arabic speaker would not be understood by an Egyptian, and a Kuwaiti Arabic speaker would not be understood by a Syrian, etc. Regional dialects may have an accent, but more importantly use different words and may even have different, informal grammatical rules.
When it comes to writing, everyone uses Arabic letters, but each region may write different words depending on the regional dialect.
The entry on Tunisian Arabic[1], which is my native dialect, may provide an idea on how it differs from other dialects.
Read the first two paragraphs for a better idea of what I'm talking about: https://en.wikipedia.org/wiki/Varieties_of_Arabic
But yeah, it's similar to the Arabic situation, but the scale may be different.