Problemm with incoming transfer from centrex PRI

I Have two problemm :

  1. Every so often my ext member received incoming call wrong number from centrex (PSTN) PRI, we have 1 ext (# 2555422) every so often received incomming call wrong number, the caller always want call to # 2555190 & 2555181
  2. When calling in middle conversation the cal drop

Pls help me for fix that problemm