OCTET 8291 Public network serving local user

Hi all,

I would like to request your help in understanding a disconnect cause that I'm currently melting my brain on.

Scenario: A# is calling B# and I get the disconnect cause as "userbusy" in my trace.

Actually, the customer says that this is not a one time issue and it happens quite often even though he's with coverage and is available to receive calls.

I've been studying this for some time and this is the conclusion I have reached:

I receive information that the B# is busy.

busyCause: 8291 .... 0010 = Cause location: Public network serving the local user (LN) (2) .00. .... = Coding standard: ITU-T standardized coding (0x0) 1... .... = Extension indicator: last octet .001 0001 = Cause indicator: User busy (17) 1... .... = Extension indicator: last octet

I've checked the octets, 8291 and:

82 gives me the general location of the disconnect (82 is Public network serving local user) 91 gives me the cause (91 is Transit network does not exist)

Looking into what "Transit network does not exist" info means, I see that in CIsco troubleshooting I get the following info:

"No route to specified transit network (national use) Indicates that the gateway is asked to route the call through an unrecognized intermediate network.".

So currently I'm on a dead end since I cant assume where this disconnect event is coming from. Is it from the RAN or from the Core.

PS: I work on an MVNO and I'm quite a noob. :)

Many thanks guys!