@eric_cranston That's the exact same problem, amongst many others I've been having on O2 as well. Good description and the same one I used to O2 about sounding like a Dalek! Often there appears to be no dip in signal strength, my network appears to be the common problem, as it happens if I ring landlines or mobiles, and probably happens on about 1 in 6 calls in the area between Aylesbury and Oxford. Other times the line will just go completely dead, sometimes it will come back eventually, other times it cuts off, other times there appears to be no chance of it coming back so you have to end the call, once again, no apparent dip in signal shown on the phone. This has probably been happening for the last 2 to 3 weeks.
I've also been suffering for months with calls not getting through to my phone, despite having a perfect signal, it just won't ring and goes straight through to voicemail, text messages and voicemails are often delayed, sometimes for several hours. Data is erratic to say the least, and O2 don't appear to be able to find a solution, I'm not the only one apparently, but their usual suggestion is try another new SIM card and we'll replace the phone, phone number 3 and SIM card number 3, same problems, still!