Laravel Cashier Stripe - Call to undefined method Illuminate\Database\Query\Builder::skipTrial()

I'm using Laravel 5.2 with Cashier package and Stripe.

in Stripe panel - Plan section - i have setted 2 plan:

1. Basic plan with 14 day's trial
2. Pro plan with 14 day's trial

Now if i have customer with Basic plan and he finished is Trial time. He want to change plan to Pro... I'm tring:

$client->subscription('basic')->skipTrial()->swap('pro')

in order to swap tp Pro plan without Trial period. But i keep receiving this ERROR:

BadMethodCallException in Builder.php line 2405: Call to undefined method Illuminate\Database\Query\Builder::skipTrial()

I'm following the Laravel 5.2 documentation:

https://laravel.com/docs/5.2/billing#subscription-trials

Help Please!!!!!