The only national express route serving Frome that appears registered as a local service is the 402 Between Frome And Marlborough. As you don?t mention The service involved, and I don?t know your area I don?t know if this is the route in question
Sort of - I will provide more data which will help (!) confirm my confusion as to whether it's local.
Prior to Lockdown, the 402 ran Frome - Melksham - Devizes - Marlborough - Newbury - London each day. Post lockdown, the 402 has not been restarted but the 401 runs Frome - Melksham - Devizes - Swindon - London each day, with lots of other 401 service running just from Swindon to London. Times are different, but the 402 went up to London in the morning and came back at the end of the day, and the 401 does the same - so clearly intended for the same passenger flows / market.