Without mutual assent, no, you cannot make any material change to the agreement.
An attempt to keep those who abide by an agreement without arms so those who disregard the agreement may gain control.
You cannot change the terms of your rental agreement except permitted by law or by the binding contract regarding the terms or conditions governing the rental agreement.
It depends on the type of agreement and the state in which it was made.
Congress can pass a joint resolution revoking an executive agreement.
Probably not. Any agreement made in writing can only be altered in writing.
The Munich Agreement signed on 29 September 1938
If they told you full service included the filter change and you agreed to full service then you agreed to a filter change and you had a meeting of the minds and a verbal agreement. If they did not change the filter they have broken the agreement.
KYOTO Protocol
no!
No.
Uh, no. Not unless both parties agree to the change.