The chart below shows how much time British residents spent on three types of telephone calls over the period between 1995 and 2002. 

We can notice[1] on the chart that the local fixed line calls slightly increased from 71 billion minutes in 1995 to 90 billion minutes in 1999. After that, the calls started moderately decreasing back to the figure - 71 billion. Similar to the local fixed line calls, the national and international fixed line calls bore an upward trend, increasing from 38 billion minutes to 61 billion minutes over the 7 years.

Compared with the mild augmentation[2] of the former two categories of calls, the mobile calls experienced a surge. In 1995, the time British people spent on the mobile calls was less than 10 billion minutes while by 2002, the total number of minutes rocketed up to 45 billion, almost quadrupled.

To sum up, though the fixed line calls were still popular in 2002, the mobiles calls were catching up. The gap between these three[3] types of phone calls was significantly narrowed from 1995 to 2002.

For my corrections red is for errors, and green for more natural language.

[1] Although you can sometimes use 'We', particularly when you are talking to an audience, and you can include yourself in those that are looking at it - I think isn't appropriate here. The 'you' form would be better. Also notice isn't a great word choice either - notice is more for less obvious things, not the main focus of a chart.

[2]Augmentation may be a little too technical for a general audience...

[3]You compared two types in the first sentence, then referred to three in the second.

I crossed out many 'the's' because they aren't quite natural here. Although you are talking about a subset of calls 'those in this 7 year period', the whole discussion is about the subset, so therefore it isn't really a selected group to refer to... Sorry if that's unclear...