Is there a way to create different SMS phone numbers for each business unit to send from?
Hi @Sparkles and welcome, we are delighted to have you here! 
Great question, thanks for asking the HubSpot Community!
To start with, I’d like to share these resources on the topic:
- Set up SMS messaging in HubSpot
- Create and send SMS messages in HubSpot
- Manage your brands with HubSpot Brands
You might want to check the third-party integrations that @danmoyle suggests in this post “Best Solutions for SMS Customer Support in HubSpot?”.
It seems that Sakari SMS has a multiple phone number options, for example, that might be of interest to you.
I’d love to ask our Top Experts also: Hi @danmoyle, @ScottPennwood and @HFisher7 do you have other suggestions to help @Sparkles, please?
Have a lovely day and thanks so much in advance for your help! 
Bérangère
Welcome to the Community @Sparkles! As far as I know fromexperience and in the HubSpot documentation, the SMS number generation process appears to be tied to the overall account and not directly to individual business units. So the short answer in a standard HubSpot interaction is no. However, as @BérangèreL mentioned there may be third-party solutions that can help. Or you’d have to use separate HubSpot accounts rather than business units.