News wrote:

We have rarely, if ever, received SMS messages on our landline phone
until now. Son's school have started sending updates by that method,
which is OK, but is there any possibility we will be charged for using
the service?

No, the only service I'm aware of in the UK which can charge to your
phone account as a result of receiving a call is if you "accept" a
reverse charge call (either via the operator or via 0800REVERSE)