Recieved 3 new sims mine works fine by husband and sons either no signal or drops out during calls

[Siobhan20]

My sons new sim gets no signal and my husbands is simular but he gets then drops out showing connection symbol top right

[NDuggan]

I've currently got this same issue, nothing seems to be working, sky help said turn on airplane mode and then back off, done it once worked for about a minute then said I had no service. 

although i have done thie again and so far the reception is holding up just low.