Cons:
Sheila would have opened fire unprovoked. Everyone was sleeping.
There was no blood on the phone.
Nevill would have difficulty speaking after his 2 face shots.
Nevill did not have the time to start ringing Bamber's AM at 3.00am. Sheila may fire more shots at him or someone else.
Even if Bamber did answer & go straight to WHF, he would be too late and of no use. Nine shots had already been fired.
Asking Bamber to 'please come over' was putting him at risk.
If Nevill was going to ring someone, it would be 999 for an ambulance. Himself and June had been shot 9 times.
Nevill would reclaim his rifle upstairs after seeing it was Sheila.
Nevill being injured but still fit enough to ring Bamber would be able to overpower Sheila in the kitchen. The evidence is his attacker hit him multiple times & Nevill inflicted no counter injuries.