There are many sources that discuss possible connections between cell phone usage and cancer. However, multiple reputable agencies dismiss this claim as being false, based on current knowledge.
According to the Food and Drug Administration, "To date, there is no consistent or credible scientific evidence of health problems caused by the exposure to radio frequency energy emitted by cell phones."
The American Cancer Society corroborates this information. Their website includes, "Cell phone use, even for more than 13 years, was not linked with an increased risk of brain tumors, salivary gland tumors, or cancer overall, nor was there a link with any brain tumor subtypes or with tumors in any location within the brain."
This particular long-term study did not reveal a connection between cell phones and cancer. However, with cell phones being relatively new, the passage of time and further studies may reveal new information.
The American Cancer Society also states "Studies of people published so far have not established a clear link between cell phone use and the development of tumors. However, these studies have had some important limitations that make them unlikely to end the controversy about whether cell phone use affects cancer risk."
Sources:
https://www.fda.gov/radiation-emitting-products/cell-phones/scientific-evidence-cell-phone-safety
https://www.cancer.org/healthy/cancer-causes/radiation-exposure/cellular-phones.html