How many simultaneous calls can my 0800 number handle?

That's governed by the SIP lines on your FreeVoIP account, not the Freephone number.

A free account includes two SIP lines (two calls at once). Since Freephone numbers on adverts can spike, many businesses move up to the 25-line SIP account at £25/month.

Match your line count to the busiest minute a campaign might create, and send any overflow into a call queue so extra callers wait with music on hold rather than a busy tone. Add lines from My Account — the number itself never changes.