There are several ways to say in a formal way that you have received a text or email. Here are a few examples:
1. Thank you for your message. I confirm that I have received it.
2. I acknowledge receipt of your text/email and will respond as soon as possible.
3. This is to confirm that I have received your text/email. Thank you for contacting me.
4. I would like to inform you that I have received your text/email. I will review and respond accordingly.
5. Thank you for reaching out. I have received your text/email and will be in touch soon.
Remember to always use polite language and proper grammar when responding in a formal setting.