what is a good call to action on postcard marketing

Our company has a platform and managed service for SME that allows them to communicate with customers on (social media, SMS email) create an online presence (with reviews, deal and events pages) and merchandise center (to post products and services for sales and such)

Our strengths is helping business owners to put together the site, the business information, manage the products listed and communication made over social media channels.

We offer a do-it yourself service, where a knowledgeable business owner that has the time for it can manage his business and offer free training once a month, and for the busy business owners that want someone to do the work, we provide a managed service.

Now we are planning to send a postcard campaign to new businesses and want to focus on the managed service clients. We are trying to figure out what makes more sense in terms of a call for action on a postcard.

We are considering the following actions:

• "Call me back" form: (URL and QR form)
• "Let us Help" : Call a Number to Order: (a rep will take the info, and have an agent call them back)
• "Sign Up" form with paypal payment!

Has anyone any experience in postcard marketing and what were best practices when it comes to call for actions?

Thanks in advance.
Adonis

It's impossible to say: no one has the answer and you shouldn't take anyone's opinion as a definite because everyone's product and target market is different. What may have worked for company XYZ 3 years ago may not work for you today. It seems that you offer your prospects 3 possible ways to interact with you: URL and QR, phone, and online ordering. So instead of picking one channel at random, I recommend you send three small sample batches of postcards, each with just one call-to-action, and measure how well each option performs for your particular service. That way, you'll know which option actually works and then you will be able do a bigger batch with just that option. Also, I'd recommend you have the postcards designed by a professional designer with previous experience in postcard marketing.