Write text messages is not available for Apple devices. It is possible to write messages into Android phones, but no into Apple devices.
For details, please look up your specific phone and its available functions at www.mobiledit.com/phones
The MOBILedit platform is renowned for its wide range of support for many devices. If the feature is not supported by MOBILedit it is very likely that it is not allowed by the manufacturer.
To investigate the wide range of functions that are available for your phone please download the free Lite version of MOBILedit at the link below and connect your phone.