Combine two sum statements in chart expressions

[qlikuser22]

HI

I am new to qliksense. I have two different datasets in QVD format, I have loaded the data and trying to create a bar chart. I need to calculate the data used from both the tables. 

I used this expression,

=((sum({$<ChargeName= {'ABCD'}>} Qty)) / 1024 + sum([MB])/count(distinct [Phone Number]))

I don't receive an error. But I have a filter for both the tables. Like Table1, Table 2. 

So if I select Table 1 filter I need the graph should show =(sum({$<ChargeName= {'ABCD'}>} Qty)) this details with respect to DATE field. Similarly for table2. 

Please do help.