How come my iphone keeps saying this?

You have been blocked from network use i just put money on it today btw its a iphone 4s pay as you go

Did you buy it second hand?
sounds like the previous owner hasn't paid their bill, and now the phone has been blocked!

Because you have been blocked from network use. Which word do you not understand?

Unsure. This would be a question better answered by your carrier.

Ask your carrier