123,047 CCS over 24 hours, that’s nothing. As you said, that’s only 142.5 erlangs !
So there is a glitch somewhere, le’s see…
1/ Why do you think you need to increase your capacity ?
2/ How many channels in one of your trunks ?
There is, it seems, a mistake of a factor “4”. So I believe that one you say “trunk”, you actually refer to an E1 nibble (16kb/s)
While a call in your system seems to be actually using 64kb/s timeslots.
Therefore you need 161 * 64kb/s, which translates in 161*4 “trunks”, which is 644 trunks. Now, there is a 80% load limit, so you actually need 805 trunks (644/0.8).
Let me know what you think.