I think data provided by you is not sifficient for the calculation of trunks. You should provide information like percentage of internal call and calls going or coming into the system i.e. the Call distribution ratio.
If we assume that 70% calls are the external call i.e. incoming call from external world and going out of the system then we can say 329 trunks are needed.
No. of subscriber=3008
Total traffic=3000×0.125=376 Erlang
Assuming 70% Traffic is incoming/outgoing for the system and 30% calls considered as internal calls then required trunks are given as:
I think these figures are right. I want opinion of others also.