Trivial Landline phones Has 2 bugs.

[Natsumehack]

Land line Phone's Headset Can be duped by quickly taking it off the base,and putting it back on over and over again .  If you keep doing this at some point another one spawns at your feet,this also makes calling with the phone impossible. You Could in theory dupe the phone headset a unlimited amount of times.

By calling another landline phone,and then stuffin the phone headset   into a microwave, you can still hear the person on the other end as if you have the Phone Headset in your hand no matter how far away from the microwave you walk.

[Kovirii]

Not sure if this is intended, but if the receiver is in your non-active hand they other party will still hear you (I think?) but it won't be show up on your end with the colored phone location.