Email Subscriber Conversion: Convert your email subscribers to SMS subscribers by offering unique content or deals via text.
Incentives for Numbers: Offer discounts or exclusive deals in exchange for phone numbers.
Checkout Page Invitations: Use the checkout page to invite customers to join your SMS list, maybe with a promise of future discounts.
Contests and Giveaways: These can be great for collecting numbers, just ensure the prizes are relevant and enticing.
Loyalty Programs: If you have a loyalty program, require a phone number for sign-up.
Always ensure clarity in your messaging about how you'll use the numbers and include options for opting out. For a more detailed guide and additional tips, check out Claspo's
https://claspo.io/blog/collecting-phone-numbers-7-useful-tips/ article on collecting phone numbers