signal on my blackberry on orange has gone

since the tmobile merge, on my wits end with them now as only manage on average a 2-5min call before I get cut off yet still both phones in the call have ok reception and end up recalling them about 10 times before I totally give up. Going to go in later today and speak to them as I'm fed up with the lack of signal just everywhere in general and the time it takes to refind signal is very poor, takes a few minutes as other people have said above...