post
https://ssg-portal-staging.melroselabs.com/mgt/v2/smpp-accounts//inbound-msisdns
Same as Routing > Inbound SMS > Add MSISDN. Routes inbound (MO) SMS addressed to this number to the customer SMPP account identified by system_id.
The number is stored as digits only. Returns 409 if the MSISDN is already assigned on this SSG.
