Corrected entry: In addition to Finney not being seen cutting the phone's cord (and not having anything to cut it with), the part of the cord that he held was longer than would be expected (even giving allowance for stretching). Also, the phone line that was attached to the wall phone was black before it returned to off-white. (01:27:00)
Aerinah
5th Oct 2022
Correction: We do see Finney cutting the phone cord; as soon as he hangs up with Robin he uses his toy rocket ship to strip and rip the cord. Also, throughout the film the spiral phone cord is always several feet long (even when not stretched), and we see him rip it about halfway down, so later it is not longer than would be expected.
Aerinah