It may surprise you to learn that, much like your computer or laptop, your cell phone can become infected by viruses and other malware. Just as with your computer, you can purchase anti-virus programs for your cell phone. However, these programs may not be able to detect and/or delete the virus that is on your phone. This doesn't necessarily mean that you have to purchase a new cell phone. There are a few things you can do to attempt to remove an undeletable virus from a cell phone.
Format the memory card in your cell phone. It may actually be the memory card, not the phone itself, that is infected with the undeletable virus. On most phones, you can format the memory card directly from the phone by going to the "Options," "Settings" or "Tools" portion of the main menu screen on your cell phone. Consult the manual that came with your phone to learn exactly how to format the memory card in your cell phone. You can also find these user manuals directly on the manufacturer's website.
Buy a new memory card for your cell phone. The undeletable virus may have damaged your memory card beyond repair. If formatting the memory card didn't fix the problem, getting a brand new memory card may fix your problem. These memory cards are relatively inexpensive and can be purchased at just about any store that sells cell phones.
Format your entire cell phone. If getting a brand new memory card hasn't fixed your phone, formatting your cell phone should remove the virus and every other file on the phone. Before you attempt to format your cell phone, remove your memory card. Read the manual for your specific cell phone, as the instructions for formatting cell phones vary based upon the manufacturer of the phone.