Activation volte huawei p20 pro

Good evening, I subscribed to a subscription on the Cdiscount site and since then I have been affiliated with Nrj mobile with the use of the network of the operator Bouygues Telecom. I have noticed that I can no longer use the internet when I am on a call, I have read some answers on your site which refer to a “Volte 4G” option that should be activated but I cannot find how to benefit from this last. Thank you in advance for your answer. Cordially