THE TELEPHONE NUMBER YOU HAVE DIALED IS TEMPORILY NOT IN SERVICE?

yesterday, i was doing buisness with this people, there telphone was working fine so we meet up and stuff and after im done with them i pay, they still owe me something. i go to call again few minutes laters in not in serice anymore, and now its not in serive today, what does this mean? did they have a non contract phone and run out of minutes? its most likley not cuase they cut it off themselves cuase they cant that fast or it cant be a conisidence the contract or payment was late. will there telephone number get removed? i cant contact them ever again.