Mapping tickets into OTRS from old system

[kmdot]

Hi

Trying to get all old tickets from our old system to OTRS, and its all gone well with one exception, the response time!

I have added an outbound phone call to all tickers, to get a response time, and set the date stamp to the data stamp when the original response went out, but for some reason its not updating.

So What I am asking is, how can I modify time stamps for response times.

Some response times are months overdue, and need to get this sorted for clients viewing reports.

Thanks