How do I join 2 conditions in Refine

I have Mobile Number column and need to check for validity for the starting number as '9' or '8' or '7'. How to achieve this if(startsWith(value, "9"),value,"Invalid Mobile") if(startsWith(value, "8"),value,"Invalid Mobile") if(startsWith(value, "7"),value,"Invalid Mobile"). In a single Text Transform, how to implement this. Please help.