AT#PDPAUTH?
Read command returns the PDP authentication parameters, excluding
<password>, set for every PDP, in the format:
#PDPAUTH: <cid1>,<auth_type1>,<username1><CR><LF>
...
#PDPAUTH:<cidmax>,<auth_typemax>,<usernamemax><CR><LF>]]
AT#PDPAUTH=?
Test command reports the supported range of values for parameters
<cid> and <auth_type> and the maximum allowed length of the string
parameters <password> and <username>.