Well... there are no Upwork rules about what information you can share with a freelancer during an audio call.
That's up to you.
If you think this information really should be logged somewhere, then use email.
If you think this information should be logged and recorded within the Upwork system itself, then use Upwork messenger... type the information as a text message.
Obviously if you give information to a freelancer over the phone, or using an audio communication technology, then Upwork won't have a record of that.
Whether Upwork has a record of such an exchange may matter less than you think. Even if Upwork DOES have a record of your communications, Upwork is not going to make a decision about who is wrong or who is right if there is a dispute.
Upwork is not a court of law. The only time that "evidence" found in your communications with a freelancer would come into play is if there were irreconcilable differences between the two of you, and a dispute was unable to settle them, and you both paid money to have the matter to arbitration, which is conducted by an outside party. If you think things might go in that direction, then it would better to think about who you are working with and how you can find people you trust, rather than focus on how to record evidence of the instructions you provided to a freelancer.
