Loss of synch, which is what it appears is the problem here, is not down to Plus Net. This is purely a BT issue between your premises and the BT exchange.
It is an ADSL issue and as such has to be dealt with by by BT Wholesale. Plus Net would or should have asked you to contact BT Retail to have the voice side of your line checked for faults. If that has been done and no fault has been found then its on to the next stage in the process.
Loss of synch can be caused by dodgy or failed adsl filters, poor internal wiring, and line faults.
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