It is tough to say exactly what is going on without a lot more information. Is this a new phone you've just activated, or is this in an area where you typically get better speeds? If you look at the bars, is there a small H, 3G, E, or G there?
It is possible you are just in an area where you have a weak signal, or where you can't get 3G/4G. If it is an area where you normally get better speeds, it could be a tower outage (usually fixed in hours). It could be there is some type of equipment, or even a building, that is causing interference with the signal. There are a lot of possibilities here.