When Fatia, 25, leaves her home to sell sex in the grungy hotels and hastily parked cars of the Ugandan capital, Kampala, she keeps her hand clenched around her phone.
After three years, her biggest fear is not violent clients or exposure to HIV, but harassment by Kampala's police.
"The police start charging you. They say it (prostitution) is not allowed in the country," Fatia, who declined to give her full name, told the Thomson Reuters Foundation in a phone interview.
"Some policemen even use you (for sex). They don't pay you and then still they take you to the station."
If arrested for prostitution, Fatia knows what to do. Call the emergency number for Lady Mermaid's Bureau (LMB) - a sex workers' advocacy organization - and beep once.
A representative from the bureau soon arrives at the station to gently remind the police that harassment or bribery of any citizen, even a sex worker, is illegal.
If that fails, she may invoke the name of one of Fatia's influential clients to scare the police into releasing her.
Gentle persuasion generally works.
Ugandan police spokesman Andrew Felix Kaweesi denied systemic police harassment. However, he said instances of misconduct by individual officers was possible.
"The police have no policy of harassing the prostitutes on the streets," Kaweesi said.
"Those who are victims should report to our professional standards unit ... Absolutely nobody will punish them. We will listen to their complaints and follow it up."
In Uganda, sex work is illegal and highly stigmatized, making women like Fatia vulnerable to unlawful arrest, rape, bribery, beating and murder, rights groups say.
The Indigo Trust, a UK-based foundation under The Sainsbury Family Charitable Trusts, gave Lady Mermaid's Bureau a grant in 2014 to help Ugandan sex workers fight abuse using technology.
It has provided around 1,000 sex workers across Uganda with information-loaded digital memory cards so they can use their phones to learn how to protect themselves against violence, HIV/AIDS and unwanted pregnancies.
The material is available in multiple languages, and in written and video format, to maximize the number of women who can access it.
"They read them, follow them and do their work safely," said Oliver Musoke, executive director of Lady Mermaid's Bureau and a former sex worker.
The cards make it easier to reach larger numbers of women than through face-to-face counseling.
"Some women are not open (to meeting us)," said Musoke, who founded the organization in 2002 to improve sex workers' access to medical, psychological and legal services and to educate them about sexual health and the law.
"They can read and take the information for themselves."
The criminalization of sex work in the conservative East African nation makes it difficult for those living on its margins to learn about their rights.
Fatia began selling sex hoping to save her earnings for a year and go into business, selling baby clothes.
But she continues to work the streets because she cannot earn enough to escape. Most days she gets one or two clients; some days, none.
"When you use protection, they give you very little money," she said. "It's not a good job at all."
Anyone who engages in prostitution is liable to seven years in jail, according to Uganda's 1950 Penal Code.
The Minister of State for Ethics and Integrity, Simon Lokodo, a former Catholic priest, has vowed to crack down on both sex workers and their clients.
But it is largely poor women who are targeted.
"Harassment occurs any time because sex work is illegal," said Daisy Nakato Namakula, a former sex worker who heads the Women's Organization Network for Human Rights Advocacy (WONETHA), which promotes sex workers' rights.
WONETHA has received 85 reports of sex workers being arrested and harassed by the police since January, but says many more cases go undocumented.
Officers sometimes threaten to publish sex workers' faces in the media and refuse to allow those with HIV/AIDS who are arrested to be brought their medication, Namakula said.
Ugandan police spokesman Kaweesi denied these allegations.
"(All) suspects have full rights of access to their relatives, access to medical attention, access to meals," he said.
Musoke of Lady Mermaid's Bureau, which has worked with more than 12,000 sex workers across Uganda, believes she is slowly changing Ugandans' attitudes.
One policeman recently asked for a memory card to learn more about the situation of sex workers in the community, LMB reported.
"I have passed through that life," Musoke said.
"I know their problems... That's why I decided to create (Lady Mermaid's Bureau), to let them know that they are also human."