Make sure it's dated and have your agent take a picture of it on the door.Then have your agent hire a locksmith to be at the property on the stated date with any necessary contractor.

Or they can try to find a locksmith (we only have two in this area) and pay $40 - $60 to get in.

If tenants get locked out, again call a locksmith and have the tenant pay for it. 

Each tenant move out you save money by reprograming the lock to a new key vs having a locksmith change the locks. 

They called me back and told me they had corrected the error and would serve another notice to the Tenant within 72 hours of the eviction (Sat morning) and it would sstill go thru at the assigned date of Tuesday.Tuesday morning 30 minutes before the eviction,  I was driving to the unit as the Sheriff had instructed me to bring a locksmith the break the lock - in case the tenant had changed them, then change the lock as soon as the Deputies had cleared the unit of people. 

I typically wait at the property until the locksmith or handyman has rekeyed the entire property.

A yes-or-no questionIn this place known for its breakneck expansion and the new nickname “Silicon Desert,” eviction is its own thriving economy.Evictions make work for attorneys, for locksmiths, for self-storage centers, for moving companies and for government staff.

Quote from @Albert Blair: If you hire a locksmith to rekey, it will likely cost you more than changing out the locks yourself.

Have them send you the invoice from the locksmith, then call the locksmith and see what the full story is.

If the tenants are completely uncooperative, I would just give them notice that I will be entering to do work and I would have a locksmith get you in and have the locks replaced at that time.