Will I be charged 25p for every test text, during development?

If you're signed up with a Basic account, yes.  But remember if you're developing a web hook, you can test almost everything independently of Taykt by calling your application with cURL or similar tools. You only need to send a text if you want to do an end-to-end test.  See: Testing web hooks

 

Could the content of the "FREE MSG" text potentially be changed, at least for a premium account?

If you're on a plan that charges consumers 25p when they text in, then we do need to send out a free info message to explain to consumers what they are using, and offer a contact number.   If you're using a plan that does not charge consumers, the message is not set.

The content of the message is currently set by Taykt, but we're happy to talk to you about what you need.