being forced to use an unverified app for work

[sneeksby]

Hi, I sub-contract for a large parcel delivery company & as part of my contract i have to use an unverified (by google or apple) app to fulfill my daily duties. I have requested to view the company's policy regarding this app & GDPR as the app contains customers details, name, address + contact details etc. The company have ignored my requests except to say "we have one but we cannot locate at present". My main concern is, these customer details are my responsibility while in my possession & the app is insecure! is there anywhere else i can take my concerns to? as i am getting nowhere with the company. Any advice gratefully received. Thanks..