California - We decided not to renew our tenants lease and sent them a certified letter stating that fact. They called us and said that since we weren't renewing the lease, they were moving out early and was only paying 1/2 the rent and to use the deposit for the rest. Although the letter stated that they needed to give us a 30-day notice and they could not use the deposit for the rents. They are gone, but will not give us the keys because they are stating that they paid thru the end of the month. Although they didn't give us a notice, didn't pay full rent & the letter informed them that they coudn't use the deposit for the rents. We need to go in and clean and would like for our new tenants to be able to move in, but the old tenants are trying to hold on to the keys, although they have nothing in the house. They moved water and waster, but not eletricity because they still owe them money. They left a small item in the garage & stated that they weren't sure if they wanted it or not. We have keys as well, but I just want my keys. What are our rights for changing the locks?