Can you block a number from calling or texting your iphone?

My friend is having trouble with someone texting and calling her. It's not a telemarketer, just an old friend who she doesn't want to hear from anymore. Is there anyway she can block him from calling and texting her iphone? Any help greatly appreciated.

Added (1). In Australia on the Telstra network.

Added (2). Also Chrissy, she tried your suggestion but couldn't work out how to do it?

Yes add number and then go to options and click block calls.texts however, no

Depends on the carrier… If it happens to be Verizon you can log onto verizonwireless.com and access your online account. From there you can block numbers… I would assume other carriers would have the same process