Cellular phones, also known as mobile phones, come in various types ranging from basic calling devices to smartphones. While basic phones still dominate worldwide, smartphones are growing in popularity due to their ability to send texts, emails, and store files in addition to calling. Major phone companies are constantly competing for market share in the multi-billion dollar industry. Recent attempts by companies to merge, such as AT&T's bid to purchase T-Mobile, have been blocked to preserve competition and consumer choice of service providers. Improper disposal of old cell phones poses environmental risks, so recycling is encouraged.