In case of Text mode, if there is a received message in location <index>, the output has
the following format (the information written in italics will be present depending on +CSDH
last setting):
+CMGR:<stat>,<oa>,<alpha>,<scts>
[,<tooa>,<fo>,<pid>,<dcs>,<sca>,<tosca>,<length>]<CR><LF><data>
If there is either a sent or an unsent message in location <index> the output format is:
+CMGR:<stat>,<da>,<alpha>
[,<toda>,<fo>,<pid>,<dcs>,[<vp>],<sca>,<tosca>,<length>]<CR><LF><data>
If there is a Message Delivery Confirm message in location <index> the output format is:
+CMGR: <stat>,<fo>,<mr>,,,<scts>,<dt>,<st>
Validity Period; its format depends on SMS-SUBMIT
<fo> setting (see +CPMS):
1. Not present: if <fo> tells that Validity Period
Format is not present
2. Integer: if <fo> tells that Validity Period
Format is relative
3. Quoted time-string type: if <fo> tells that
Validity Period Format is absolute
4. Quoted hexadecimal representation of 7
octets: if <fo> tells that Validity Period Format
is enhanced