In BSC Configure Service Negotiation window, there's an item namely "Enforce Strict Priority Order" on top right corner.
If uncheck “Enforce Strict Priority Order”, AAC2K will compare device proposed SO/RC with its BSC setting and choose a matched one.
If doesn’t find a matched one, AAC2K will choose default SO setting.
e.g. when uncheck it: if device proposes SO33 and BSC sets to SO3, they don’t match, so AAC2K chooses default value SO33 for data call. This explains why SO33 call sets up sucessfully.
If check “Enforce Strict Priority Order”, AAC2K only negotiates configured Service Option in order.
e.g. if only configure SO3 in BSC, AAC2K will reject all the other SO. This way SO33 call will fail.