You'll want to do both:
How do I use the "Busy Line Call Forwarding" feature with my Cricket phone nuraber?
To use busy line call forwarding, complete the following steps:
1. Dial *73 followed by the ten digit phone nuraber (555-555-5555) you would like your calls to be forwarded to.
2. Press the SEND button.
3. You will hear a tone and your call will terminate automatically.
4. All incoming calls to your Cricket phone nuraber will now be forwarded to the nuraber you selected.
5. To turn the feature off, dial *730 and press the SEND button.
6. You will hear a tone and your call will terminate automatically.
7. You will now receive calls as normal to your Cricket phone nuraber.
[-] How do I use the "Call Forwarding No Answer" feature with my Cricket phone nuraber?
To use call forwarding no answer, complete the following steps:
1. Dial *74 followed by the ten digit phone nuraber (555-555-5555) you would like your calls to be forwarded to.
2. Press the SEND button.
3. You will hear a tone and your call will terminate automatically.
4. All incoming calls to your Cricket phone nuraber will now be forwarded to the nuraber you selected.
5. To turn the feature off, dial *740 and press the SEND button.
6. You will hear a tone and your call will terminate automatically.
7. You will now receive calls as normal to your Cricket phone nuraber.
http://www.mycricket.com/support/search/forwarding