Hmmm.. That can be quite annoying especially during times that you need it the most.
How long have they encountered this issue? When did it started? There are a lot of factors that can affect data signal. It can be environmental (building structure, building material, etc.), it can be with the device, it can even be because of the time of the day (congestion).
If the issue persists, I suggest that you contact Globe's Customer Support at the URL below:
or you can also tweet them @Talk2Globe
Hope this helps