Cannot Connect to the Internet Using Mobile Data

Hi,

I've been using WIFI for my internet connection on the mobile phone for a while now but unfortunately I have recently had to cancel my WIFI provision and now I'm relying just on mobile data. 

I'm basically unable to connect to the internet in the main however sometimes I can get a connection but it is very slow and intermittent (unusable).

There is coverage in my area and no current outages so I'm wondering if Smarty doesn't have a "strong" signal where I live and I need to change provider? It could be that I haven't set the connection up properly though (or some other setting)  so I'm asking for any hints or tips anyone can provide.

Thanks in advance.

D