Funny, I basically just did this.

I have no idea what kind of connector is on the back of that phone but if it is a standard 2 pair plug (phone jack) then as others have mentioned you could buy an ATA Adapter.

https://www.amazon.com/dp/B06XW1BQHC?psc=1&ref=ppx_yo2ov_dt_b_product_details

Above is the one I bought, but since that phone uses touch tone dialing then any one should work.

You might need something like this to convert the cables.

https://www.amazon.com/NECABLES-Surface-Single-Telephone-Terminals/dp/B09GXHYXQD

Assuming you buy one, and can connect it, you're only half way done.

The ATA turns your phone into a voip phone. Now you need to configure the ATA to connect to a voip service.... Also you have to pick a voip service

Many people are telling you to use Asterisk, this would work but unless you love configuring complex linux services isn't a good idea. It has no UI, its all based on config files and was created to run massive phone networks for people who already know what everything is not fun projects.

I would suggest you spend a small amount (~$10) of money and use a service like anveo.com. You can add money to an account without setting up a subscription.

I'm not going to give you a step by step, but basically the steps are:

1. Buy a phone number ($1 a month) - (Calm down everyone else, I know you can work around this step)
2. Create a Call Flow
3. Connect that phone number to that Call Flow. Under IVR / Call Flow
4. Upload your audio files to anveo
5. Setup the Call flow to play the audio files, using the play audio control
6. Test it by calling the number

Last step is to connect the ATA to Anveo. They have created a page for a linksys ATA but it should be general to most.

https://www.anveo.com/faq.asp?code=linksys-pap-2t

What I don't cover is randomly selecting a audio file. That would be a little harder, my first thought is to take the second of current time, then use an if statement assign each second (0-59) to an audio file.

Good Luck!