A simple tip

Toyota Proximity key front and back

Remove the concierge key

With a knife or screwdriver prize it open

there is the battery (Open from the back)

Here is something you can do.
Do it while sitting at a table so you are in control.
Try to get batterys with corresponding make and numbers I got 10 for £12 from Amazon.
Once upon a time I was told by a garage that they would need to replace the battery in my key.
They wanted £20, I just popped over with the spare key and when I checked the "Faulty" key fob they had taken the battery out..

One last thing. On a hot summers day you took off your jacket and threw it into the boot of your Porsche
You close the boot and the car locks itself ??????? They do that !
The keys are in your jacket pocket now locked in the boot and you are locked out.

Try this. Ring home and ask someone there to get the spare key from the desk.
Now for a drum role .
"Hold the key to the phone and when I count to three press the unlock button on the keys"

You turn your phone to speaker and hold it to your lock the magic begins

Not every car will pop open, sometimes you will have to do it twice

Worth a try anyhow.

always have a spare key if you have only one key and it is put in the washing machine the replacement process is around €2,500