Get a local SIM

Get a local SIM. They are really cheap and £5 of credit will last at least a month. You can buy a top up card from pretty much any stall, including shoe cleaners on the street. If you bring an old phone, then put the SIM in that so a) you won’t be using a flashy phone in public and tempting thieves, and b) you can download the app RIDE, the Ethiopian equivalent of UBER, and is cheaper and safer than normal taxis, and you can get picked up from anywhere.