No I mean a registered "С регистрация" but unactivated SIM which can make voice calls.

I fear that "registered" SIM cards are activated automatically upon registration and so the beginning of the activity time frame cannot be retarded.

Ha! That means my telephone connected to a Greek network as well when I was near the border. And I see why google translate didn't want to work. Anyways, we know now that it's no problem recharging unregistered cards from abroad :)

I discovered that M-Tel's 12-month validity period starts from the date of the first call. They also charge double (BGN 19.90) for a nano-SIM or micro-SIM, but it includes 512MB of data and a discount on national calls (BGN 0.39 per minute) for 90 days.

Finally Vivacom has introduced data bundles that can be added to all their prepaid SIM cards (as opposed to special data-only SIM cards): +Get Data, Mobile Prepaid, Mobile Services, Prices & Services, VIVACOM

The only interesting bundles are the larger ones:
L 150MB valid for 30 days for Lv 14.99 (€ 7.66)
XL 750MB valid for 60 days for Lv 19.99 (€ 10.22)

Currently both data options are available free of charge if you recharge your SIM with Lv >=20 or Lv >=49.99.

These data tariffs combined with the "VIVA International" SIM card which provides reasonable international voice rates is probably the best choice for visitors who don't require too much data volume.
Remember that much of Vivacom's 3G coverage is based on UMTS900 which is not supported by all handsets.

Currently, as of mid-July 2013, M-tel has the shittiest network out of the 3 top BG operators.

Since I'm traveling around for about a month and really need a descent connection, I have gotten 2 prepaid cards from 2 different operators -
- M-tel Prima (1.5GB package for 29.90 Leva) and
- Globul GoWeb (1.0GB for 29.90 Leva).

I'm using both of them for half a month already at various places in Bulgaria (Sofia, Varna, some rural places at the southern Black Sea beach, etc.) and have to say that Globul's coverage is pretty descent - HSPA everywhere, no packet loss and good packet round-trip times (like ~100ms from here to Germany).

M-tel's network is really *horrible* - low signal strength, connection frequently bouncing between UMTS/HSPA and EDGE, almost half of the packets getting lost or delayed for several seconds (!). Round trip times to google.com for example average at about 2,200ms. It looks like it's constantly overloaded, regardless of location and connection speeds. Since I need reliable interactive sessions with good response times, M-tel's network is practically unusable for me.

I have no opinion on Vivacom's network yet, but likely will ditch M-tel and get a Vivacom sim card as a backup next time.

New Globul prepaid product: Prepaid data package GLOBUL GoWeb 2000
 

Globul has a Prepaid SIM card for data only usage, announced als "new". The user gets 2 Gigabytes for 9.90 BGN (5.05 EUR). I bought one from a Globul store. The whole process including activation took five minutes. The shop assistant did the activation immediately. The SIM card works in my phone without any problem.

An ID is nessecary but neither a Bulgarian nor a home address is registrated.

The 2 Gigabytes may be used within 7 days from the time of registration.

Please provide updated info
 

Will be traveling to Bulgaria withing 3 weeks.
What is the recommended prepaid SIM card for data only?
I estimate I'll be using about 3GB.

Thanks.

Daniel

Hi Daniel.
Here is a market survey. It should be more or less up to date:
http://prepaid-data-sim-card.wikia.com/wiki/Bulgaria
For data only, it's sufficient to choose a data SIM card like Prima Data from Mtel, GoWeb 2000 from Telenor or Easy Traffic from Vivacom. It has enough start up volume, for 3 weeks you going to add a bundle.

Thanks
 

What about registration of the SIM card?
I read in one of the providers that this is required.
How complicated is the whole purchase, activation and registration process going to be?