Customer has Norstar MICS 0x32 KSU with 7.0 Rls Software. Problem is that some of the phones are displaying Numeric characters instead of Alpha numeric characters on their displays. I recycled the power and seemed to have cleared the problem but customer informed us that problem is back. Is software possibly corrupted? Should we replace KSU and upgrade to 7.1 Rls. Software? Customer has PRI and advised them that they will lose PRI key code. Please advise.