Just to remind people these two decided to phone someone they didn't know, who was newly pregnant and ill enough to be in hospital for days. They didn't know the extent of the patients condition, but it had been widely reported it could lead to serious implications for the mother & child.
And with that knowledge they decided as a joke to phone and speak to a sick patient The full length version of the call
broadcast was promoted as an attempt to speak to the patient. The first words uttered by Mel Greig was, "Could I speak to Kate please."
That was their objective, nowhere do they say we didn't expect to get through...they were basking in the glory of the call, it was only after it went pear shaped they modified their story.
The call was not broadcast live, it is possible what was broadcast was not the full extent of the call, it may have been edited to make good radio.