In case of TEXT mode, the representation format for stored messages
(either sent or unsent) or received messages (either read or unread, not
message delivery confirm) is:
+CMGL:
<index>,<stat>,<oa/da>,<alpha>,<scts>
[,<tooa/toda>,<length>]
<CR><LF>
<data>[<CR><LF>
+CMGL:
<index>,<stat>,<oa/da>,<alpha>,<scts>
[,<tooa/toda>,<length>]
<CR><LF>
<data>[...]]
The information written in italics will be present depending on +CSDH
last setting.