I signed their $10.10 for 40GB plan at a retailer shop this January. All good until June, since then the connection becomes bad. I believe many ppl have mentioned Serangoon MRT, me also experiencing no network there. CCL very poor coverage. In NEL and EWL it can connect to network, but TBH the speed is relatively low, at non-peak hours hard to watch 1080p video or open pictures on social media.
This is why I decide to jump to Singtel MVNOs, hope it would be better. (Maybe at last I would find that all the MVNOs would suffer from disconnection in crowded places due to deprioritisation).