Petro Canada

Sensor Light came on showing a tire was low.pulled in to full service Petro Canada.
Asked for help.Employee felt front tires appeared low.Put air in both tires.I checked and advised sensor light still on.He then put more air in front tires.I noticed there was now a bulge in side wall.I advised him .I left and drove 10 minutes to my son's as employee was no help.My son's tire gauge goes to 48 PSI.After letting air out for approx 2 minutes the gauge started to register.We estimate PSI was at least 70.Established left rear tire had a nail. 2 new front tires cost $423.00.Existing tires has at least 50% tread remaining.Manager(Manzer(604-464-5040)is no help.His employee advises the bulge was already there.I would never consider driving my 2 grand kids with faulty tires.
Please help Kathy Greschner [protected] or e-mail [protected]@gmail.com