You may contact the company directly on base of the information provided by Leadinfo. After all, the GDPR does not apply to company information such as a general telephone number. Please note that sending unsolicited commercial emails or SMS messages is subject to spam legislation, even if you do so to a general number or an info@email address.
If you want to approach a person at the company, you must have a clear base, such as opt-in or a warm customer relationship, to approach companies. Just the fact that someone visits your site is not a base for emailing or calling this person. You will therefore have to have an additional reason to contact them.