White blood cells are a sign of infection, the body sends them to the site of an infection to try and mop up the infection, they are our bodies natural protector. You may still have white cells in your urine, but no bacteria, it's a sign then you had an infection.
You have every right to ask your GP to show you the report from the lab.
If bacteria are present, the report will show what bacteria it is, E.coli is the most common and the report will show which antibiotics will kill the infection and which ones will not, obviously the GP needs to pick an antibiotic that will kill the infection.
20 years working in microbiology has come in useful!!!!!