Many things about your business are hard to communicate in marketing materials because they're intangible. For example, value and customer experience are largely subjective. To help you communicate your business' trustworthiness in ads or social media, you might consider having customers give testimonials. If you choose to do this, it's important to let the customer use their own words - not only will this make for a more natural and credible testimonial, but they'll likely feel more at ease as well.
Another way to communicate trust in your marketing is to build transparency and humanity into all you do. For example, you can clearly outline your returns policy on your website, or answer customer questions honestly and compassionately on social media.
Are there ways you can concretely demonstrate your trustworthiness? How can you prove it? Maybe you have a group of long-term customers, or maybe your products have a reputation for longevity. If you can demonstrate that you have a solid product/service, it will be more powerful than just saying, "Trust us on this one."