Changing date of rent due on storage unit

[S__]

What is the name of your state (only U.S. law)? California

Is it legal for a storage unit facility to change the date that rent is due on a storage unit?

Here is the situation:
Rent for the unit is due on the 20th of each month.
(Rent had not been paid, and all proper pre-lien notices were sent to the renter.)
The unit renters received a lien notice that required payment of $310.00 by the 5th. A partial payment of $100 was accepted on the 1st.
A second lien notice was sent out on the 5th, requiring payment by the 21st.
The payment should be for the remaining amount of $210.00. But, the notice states that a payment of $285 is required.
When questioned, the storage unit managers said that the partial payment that was accepted on the 1st automatically changed the due date of the rent to the 1st of each month, so now a pro-rated rent rate plus new late fees and lien fees that reflect the change in the due date are now also due.

Is this legal?

Also, is a storage unit facility legally obligated to accept payment up until the auction time so that the renter may recover their belongings?

Thank you.

 

[JETX]

the storage unit managers said that the partial payment that was accepted on the 1st automatically changed the due date of the rent to the 1st of each month, so now a pro-rated rent rate plus new late fees and lien fees that reflect the change in the due date are now also due.

Is this legal?

Not unless allowed per the WRITTEN agreement.

Also, is a storage unit facility legally obligated to accept payment up until the auction time so that the renter may recover their belongings?

No.