I may need to call 999/101soonish but I don't have any credit. What can I do?

My friend is suicidal and he keeps trying to commit. I may need to call 999 or 101 if he tries again. I don't have any credit on my phone so I won't be able to call. I should be able to since it's an emergency service number but my phone doesn't allow me to make calls when I don't have credit. Also, the 101 number is 15 pence per minute. I really can't let my mum find out about this but if I am to call 101 it will show on my phone bill, I don't know if she looks at my phone bill but if she does, she will see. Because I don't have any credit I don't have 15 pence to make a call. Will 999 be free and will the call be able to go through?