First, make sure that you are not sending texts through a group chat because Android devices are not compatible with the iPhone's texting apps when it comes to group messages.
If that doesn't work, you might be able to find a solution by using our Troubleshoot & Resolve Tool. Just click the link, select your device, and then select Messaging under the Service/Network Issues section.
Let us know if this helps!
Cameron, AT&T Community Specialist
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