You may want to check is it your phone having problem with reception at underground mrt. Many others who have same problems here are using iphone.
I have used Circlelife for many years back, my usual mrt route travelling from JE to BV to MacPherson to Tampines East weekdays during 7-8am, no issues with data reception.
Now I am using Eight on $300+ xiaomi phone and simba on $100+ Samsung tablet. Both do not have issue on data on same route during 7-8am weekdays, surfing/post on FB, IG, shopee, HWZ.