Simple...because it's the nice thing to do.
Simply say hi to her and then ask politely to speak with your boyfriend.
Parents who speak politely to others are teaching their children to be polite, by example.
To politely ask for someone's phone number, you can say something like, "Would you mind sharing your phone number with me?"
You can politely ask someone for their phone number by saying something like, "Would you be comfortable sharing your phone number with me?"
Politely, if one has any sense.
To politely ask a friend for their phone number, you can say something like, "Hey, would you mind sharing your phone number with me? I'd like to stay in touch more easily."
Ask politely.
You can politely communicate your preference by saying something like, "I prefer not to engage in phone conversations, but I am happy to communicate through text or email instead."
The same way he talks to you face-to-face. And politely.
You can politely communicate your boundary by saying something like, "I appreciate our interactions, but I feel it's best for both of us if we no longer communicate. Please respect my decision and refrain from reaching out to me again."
To make your phone into a speak message phone you turn up the volume and press the space number. You can only make it speak if it is a phone with a keyboard or has that effect. Some phones do not have this effect.
If you speak properly, politely, and express yourself fully, then your life will be better because people will help you instead of reacting negatively to you.