If you are already using an antiperspirant and it's not working you can increase the strength by using OTC clinical strengths or getting a prescription strength, but it also increases your risk of breast cancer. If you have hyperhidrosis there are other medical options to stop you sweating through your clothes. I take Oxybutinin at the moment but I am considering Botox to avoid daily medication.
Pharmacist and doctors are just people and are susceptible to miss information just like us all. I encourage you to look into it yourself though. The National Cancer Institute and American Cancer Society both have informative articles about it because the myth is so prevalent.