Looking for a light CRM

My company makes consumable products for oil & gas. Once a customer buys one product they typically buy more on a regular basis. Our sales team is small (4 people) but we need something to help keep organized.

Right now we are just using an online excel sheet. All we really need is something to keep notes and is easily accessible on a phone. Although 50 separate customer tabs on excel is not quite doing the trick.

Is there a really simple CRM system that could accomplish this for a low price?