<s>
Ringo	B-Protocol
was	O
an	O
international	O
calling	O
app	O
for	O
smartphones	O
that	O
utilized	O
dedicated	O
phone	O
circuits	O
for	O
making	O
calls	O
.	O
</s>
<s>
Ringo	B-Protocol
used	O
local	O
phone	O
networks	O
instead	O
of	O
the	O
user	O
's	O
smart	O
phone	O
's	O
Internet	O
connection	O
to	O
connect	O
calls	O
.	O
</s>
<s>
Apps	O
were	O
available	O
for	O
Android	B-Application
,	O
iOS	B-Application
,	O
and	O
Windows	B-Protocol
Phone	I-Protocol
.	O
</s>
<s>
Ringo	B-Protocol
launched	O
in	O
2014	O
and	O
was	O
available	O
for	O
use	O
in	O
many	O
countries	O
,	O
though	O
not	O
all	O
supported	O
all	O
three	O
calling	O
methods	O
:	O
-	O
callout	O
,	O
callback	O
and	O
WiFi	O
.	O
</s>
<s>
Ringo	B-Protocol
was	O
discontinued	O
on	O
March	O
31	O
,	O
2021	O
.	O
</s>
<s>
Ringo	B-Protocol
was	O
developed	O
by	O
start-up	O
Riva	O
FZC	O
,	O
the	O
parent	O
holding	O
company	O
of	O
Ringo	B-Protocol
.	O
</s>
<s>
Ringo	B-Protocol
allowed	O
users	O
to	O
make	O
calls	O
to	O
any	O
number	O
in	O
any	O
destination	O
worldwide	O
and	O
did	O
not	O
use	O
a	O
web	O
connection	O
for	O
its	O
calls	O
.	O
</s>
<s>
Users	O
could	O
purchase	O
top-up	O
credits	O
through	O
the	O
app	O
for	O
Android	B-Application
and	O
Windows	B-Protocol
Phone	I-Protocol
and	O
through	O
the	O
website	O
for	O
iOS	B-Application
to	O
make	O
calls	O
.	O
</s>
<s>
When	O
a	O
call	O
was	O
made	O
using	O
Ringo	B-Protocol
,	O
it	O
was	O
connected	O
to	O
a	O
local	O
phone	O
network	O
and	O
assigned	O
a	O
local	O
number	O
.	O
</s>
