That only applies in the bike or walk home version of events. If he thought they could log the calls then he would have to make the call happen. Either by using a car to drive back (does not need to be his car) or before he leaves WHF and shooting his parents and the twins he then instucts Sheila to call him at Goldhanger at 3:30am. Then while on the phone JB instructs Sheila to shoot herself.
But - Sheila didn't shoot herself dead twice with the same rifle and end up like shown in the second lot of photographs taken at the scene!
She didn't shoot herself..
Her death scene was staged as to suggest that she could have taken her own life, but she didn't and she couldn't have!
She was definitely shot by bullets fired from two different weapons, where the original PV/20 was fired from one gun, and the second PV/19 bullet was fired from the anshuzt rifle!
Her body did not fall naturally into the position her body was eventually photographed in, without her body having been on its right hand side for a considerable period beforehand!
Sheila's right arm and her right hand would have been trapped beneath or under the right hand side of her body at that time, and therefore, she still couldn't have been holding onto the rifle, and it still be being grasped with her right hand resting flat on top of the gun once her body was rolled back onto its back! Not only that /this the rifle end up resting on top of her body with the muzzle of the guns barrell resting on so perfectly close to both bullet entry wounds on her neck!