Hi! You are getting a little confused between 3G and HSPA.

When telecom companies advertise their speeds, they always advertise their maximum theoretical download speed(evil marketing strategy).

A 3G Network has a maximum theoretical download speed of 7.2 Mbps(Mega-bit not Mega-byte) and upload of 3 Mbps.

An HSPA+ Network has a maximum theoretical download speed of 42 Mbps(You got confused here) and upload of 6 Mbps.

There are a number of factors that will affect your internet speed like:

Network Coverage

Your network coverage depends solely on the availability of transmission towers of the network service you are using. Not all service providers have towers that cover all areas especially in the rural areas and network service in these areas can be very weak.

Obstruction

Weak coverage can also be caused by obstructions both natural and man-made such as buildings, forests, mountains or variations in landscape which blocks signal. If the phone signals get blocked, your network coverage will deteriorate.

Network Congestion

Network congestion happens when the telecommunications networks become congested or "overcrowded" when everybody uses the network at the same time. When the network is congested, it "drops out" a ‘packet’ which can carry either a data or voice connection.