Wavering Lawfulness

[A lady customer storms into the pharmacy]
[Lady Customer] You didn't give me the bill.
[Pharmacist] < coolly > You didn't ask for it.
[Lady Customer] But you must give the bill.
[Pharmacist] Had you asked, I would have.
[Lady Customer] I might have forgotten.
[Pharmacist] I thought you didn't need it.
[Lady Customer] But you must give the bill by default!
[Pharmacist] Okay, wait. I'll give you the bill.
The present customer didn't ask for the bill. The pharmacist didn't give one.
The second customer didn't ask for the bill. The pharmacist didn't give one.
The third customer didn't ask for the bill. The pharmacist didn't give one.
Now the pharmacist turned his attention to the lady customer.
[Pharmacist] Name
[Lady Customer] < No longer the firm voice that she started with > ...
[Pharmacist] Spell it.. Doctor's name
[Lady Customer] .... Give me one more medicine
[Lady Customer] < pays for the new medicine >Take two rupees change...
[Lady Customer] Oh! It's one rupee...
[Pharmacist] Here you go...< gives the bills for the previous and the present medicines >
[Lady Customer] < ready to go >
[Pharmacist] Wait! you have to get back ten rupees change.
[Lady Customer] Oh! Thank you!