Normally, in order to collect a digital signature remotely via the text to checkout feature, you must utilize Shelterpay powered by Stripe, the integrated credit card processor. If you are unable to use Shelterpay to process the transaction and must instead use an outside method of payment (such as a different credit card processor, e-transfer, or Interac Debit cards common in Canada, etc.) or this is for a check or cash transaction, there is an alternative method.
You must still have a Shelterpay account linked to Shelterluv, but you can instead process the adoption via a texted checkout for $0 using an adoption fee set to $0 or discounted down to $0. Stripe will not charge any fees for a $0 transaction as long as a donation is not made on the transaction (the entire transaction must be for $0 total, otherwise the donation amount will need to be paid via Stripe during the texted checkout flow and Stripe will charge the normal fees).
If desired, you can then process a second transaction to represent the adoption fee using a non-adoption shopping cart item, in order to balance your accounting reports for the day. Keep in mind that this will impact how adoption fees look in reporting (you'll now have one transaction for a $0 adoption fee and one transaction for an item that represents the adoption fee); additionally, the adoption contract will show a fee of $0.
Please reach out to firstname.lastname@example.org if you have any questions about this alternative workflow.