What to say to someone who has asked for my number?

Brief background - I know I’m autistic but am still on waiting list for my assessment so I haven’t been diagnosed yet. I’ve masked my whole life and I want to start to unmask but have no idea how to start as I usually try and people please and saying no to people is scary for me right now. 

My issue/question - I messaged a photographer as I want a family photoshoot done in July. We’ve worked with her two times previously. She messaged me back asking for my number because she wants to call me to discuss my requirements. She never asked to do this the two times we previously worked with her. I have a huge huge issue with speaking to people on the phone. Like to the point where I’d rather not use her than speak to her on the phone. But I also find it impossible to say no to people because I’m so used to people pleasing to fit in. I also don’t want to tell her I’m autistic because I’ve not yet had a diagnoses and would feel like I’m not being completely honest if I told her I am (as it feels unofficial to me). I do want to use her for a photoshoot but I don’t know what to tell her. I don’t want to have a phone call. I don’t want her to think I’m weird but also want to avoid the call at all costs (I know defeats the point of unmasking but I’ve no idea where to start with that)

I know this issue probably sounds stupid and it probably seems like a stupid problem to even post on here but I genuinely don’t know how to go about this. Please help!?