Random animation duration

Phaser 3
1

Hello Phaser community ,
I am a new developer … was trying to make a simple 2D game , but struggled with some stuff
because my programming knowledge is poor …
The game Idea is
When the pointer down an animation start (BOSSTALKS)
Here is the animation code

var frameNames4 = this.anims.generateFrameNames('bossanim', {
                     start: 0, end: 26, zeroPad: 2,
                     prefix: 'bosstalks', suffix: '.png'
                     });

     this.anims.create({ key: 'bosstalks', frames: frameNames4, frameRate: 10});

Now this animation duration is the same everytime it plays … what i need to do is to make the duration randomly generated … this animation its a phone call so i need it for example to last 5 sec the first time 15 sec the second time …
Sorry for my bad use of english and thank you in advance .

2

I thought of making multiple animations of the phone call with different frame Numbers
so here its

start: 0, end: 26, zeroPad: 2

the other one will be like

start: 0, end: 40, zeroPad: 2

and so on …
but if did that … how do i call these animations to run randomly in my game
Now its only one animation and i call it this way ;

function onEvent ()
{

    
    tel.anims.play('telrings');
boss.anims.play('bosstalks');

if i made multiple animations with different frame numbers how do i call them to run randomly ?