I am considering buying a United mileage ticket that would be LAX-LHR-JHB-LHR-LAX. Because of the stopover allowance this would equal 40000 miles each way. The account I am purchasing it on has United 1k which enables free cancellation. If I were to say only fly the LAX-LHR portion or just the LAX-LHR-JHB portion would I be able to cancel the ticket and receive a full refund of unused miles, or does using one segment mean I cannot cancel?
Thanks