each nhs trust does contract out the 111 service to a different provider - some run by ambulance centres, some by private organisations. the 111 service for cornwall is by a completely different company to the one run by Hertfordshire for example. each service provider has to compete for each contact. so don't think one bad 111 means every 111 service is bad.
17 year olds are allowed, legally, to work full time in the UK. a 111 service cannot refuse to hire a 17year old based on their age just like they couldn't refuse to hire a 60 year old. it is age discrimination.
if at 16, you can join the army and fight for the country, I'm sure you can manage to answer the phone and tell someone where their nearest pharmacist is