Advice? One handset multiple lines.please help :)

Hi there,
I’m looking for advice on whether Asterisk is the solution for us. There is a mountain of info out there but I would really appreciate if someone could narrow down what I should be researching.

My wife has a hair salon with one phone line. It has call waiting (max of 1 call on hold/waiting) but she is still misses a lot of clients when three or more people call at once or the staff don’t hear the near silent beep to notify of call waiting (noisy salon!)

We have the option to get an extra line into the premises or setting up some HD voip accounts. The internet here is “fiber to the building”

Is there a reliable software/hardware/handset configuration you would recommend that would allow her to keep her current phone number and allow her to accept and place multiple calls on hold?

I really appreciate any advice

If you use PSTN lines, you will be limited in the number of calls you can have on hold. Also, Asterisk doesn’t really support holding an analogue line. You should be looking at VoIP.