To help reduce the number of declines that your client will experience there are two settings in your Stripe account that you can use to relax the measures that Stripe will emply when deciding to accept a card.
To find these options,
First log into your Stripe account at www.stripe.com
Click your account name (top right hand corner of the screen)
Choose Account Settings and the options are at the bottom of the screen.
Decline charges that Fail CVC verification
Uncheck this box if you do not want Stripe decline a card when the CVC code of the credit card is wrong when entered by the client.
Decline Charges that Fail Postcode / Zipcode Verification.
Uncheck this box if you do not want Stripe to decline a card when the postcode / zipcode of the credit card is wrong when entered by the client.
Please note that by disabling these features you will reduce the munber of declines that your clients experience but ultimately you increase your risk of fraud.