meritez Though I’m not an expert in networking in computer science, let me make a brief explanation.
VOTLE (voice over long term evolution) is the ‘new mobile network generation’ of VOIP that enables calling through packet switching(calling on 4g network) which enables clearer voice calls(better audio quality), faster network speed while making calls, better security(lesser chance to get intercepted)&lower battery consumption.
*While VOLTE only supports 4g&above it has nothing to do with missing calls or messages, its is not something compulsory, the only difference is calling through 4g network(patcket switch) or 2g-3g(circuit switch).
*Some phones also let you switch it off,
Without VOLTE your phone will go through packet switch fall back (CSFB) and drops to 2g/3g signal only while being on the line, as 4g runs on circuit switch but 2-3g runs on packet switch(default way of making calls).
giffgaff enabling VOTLE will let us stay on 4g(or 5g) while being on the line without dropping to 3g, but else the drop&recover is basically instant and you wont lost any calls/messages.
If your need an emergency call outside the city I would recommend not doing it over votle as patchy 4g coverage WILL cut your call, else, no difference.
no volte: drop to2g-3g signal while making/receiving calls
votle enabled: stay on 4g-5g while making/receiving calls
unless you hate your 2k+ quality video steaming/downloading to lag/slow down while making calls nothing lethal.