The problem
You are unable to book an easyMobile roaming option via SMS reply – request unsuccessful.
The reason
When sending an SMS booking request, some Android SMS messaging apps will automatically add Germany's international prefix. For example instead of sending your request to 70127, your SMS is instead sent to 004970127. Unfortunately this is not the correct number and will invalidate your reply and your booking request.
The solution
Deactivate the Roaming assistance dialing feature in order to maintain the required formatting. Open the telephone app on your phone and tap on the 3 dots at the top right of the screen, then select: Settings --> Other call settings --> Roaming assistance --> deactivate Roaming assistance.
After deactivating Roaming assistance, open your messaging app and send a new message with the appropriate booking text for the desired roaming option to the number 70127.