Problem on E71/S60 with SMS delivery receipts

For the last 2 weeks or so I noticed that on my E71 SMS [1] delivery receipts (or reports) quite frequently (~50% of the time) are displayed as plain text SMS, instead of hidden and just used to update the delivery status of the message.

Such a report then looks like this:

id:0010520070 sub:001 dlvrd:001 submit date:0812311708 done date:0812311708 stat:DELIVRD err:000 text:Test

This is
a) not very readable
and
b) totally useless (since the message will stay as "Pending"...)

Most annoying is, that my operator (A1) charges for the delivery receipt (equivalent of 1 SMS).

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[1] "texting" for the native speaker amongst my readers.