I got one of these last year and knew it was a scam so I text back that I thought it was a scam because you never call me mum, you always call me mummy, long story short, the text ended with them replying, OK mummy. I’m usually suspicious of these as I know what my child contacts me for and it is not a lost phone etc. Best way to deal with these is to be suspicious first and contact said child to check. Just have to be vigilant these days.