TP-User-Data
If <dcs> indicates that 3GPP TS 23.038
default alphabet is used, each character
of GSM alphabet will be converted into
current TE character set (see +CSCS)
If <dcs> indicates that 8-bit or UCS2 data
coding scheme is used, each 8-bit octet
will be converted into two IRA character
long hexadecimal number (e.g. octet 0x2A
will be converted as two characters 0x32
0x41)
If <fo> indicates that a UDH is present
each 8-bit octet will be converted into two
IRA character long hexadecimal number.
The <length> indicates text length in
characters without UDH length.